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OF

MORPHOLOGY.

EDITED BY

Cr OO. WHITMAN,

PROFESSOR OF ANIMAL MORPHOLOGY, CLARK UNIVERSITY,
WORCESTER, MASS,

With the Co-operation of

EDWARD: PHELPS ALLIS; Jr,

MILWAUKEE,

Kom! TE

BOSTON, U.S.A.:
GINN & COMPANY.
18809.

Bie

1 He

IV.

II.

CONTENTS: OF VOL. IIE

No. 1.— June, 1889.

J. Prayrarr McMorricu, M.A., Px.D.
The Actiniaria of the Bahama Islands, W.L,,

R. W. SuuFetpt, M.D., C.M.Z.S.

Contributions to the Comparative Osteology of
the Families of North American Passeres,

R. W. Suuretpt, M.D., C.M.Z.S.

Notes on the Anatomy of Speotyto Cunicu-
laria Hypogea .

James I. Peck, A.B.

Variation of the Spinal Nerves in the Caudal
Region of the Domestic Pigeon

No. 2.— September, 1889.

E. D. Cope.

The Mechanical Causes of the Development
of the Hard Parts of the Mammata .

WittiAmM M. WHEELER.

The Embryology of Blatta Germanica and
Doryphora Decemlineata

PAGES

1-80

8I-114

T15-125

127-136

137-290

291-386

it.

RIT,

LV

CONTENTS.

No. 3.— December, 1889.

EpmunpD B. WILson.
The Embryology of the Earthworm

Dr. G. Baur.

On the Morphology of Ribs and the Fate of
the Actinosts of the Median Fins in Fishes,

Dr. G. Baur.
On the Morphology of the Vertebrate-Skull .

kW. SHUFELDT, M.D, CM.Z.S:
On the Position of Chameza im the System.

TyrocrarnHy By J. S. Cusuinc & Co., Boston, U.S.A.

Presswork sy Ginn & Co., Boston, U.S.A.

PAGES

387-462

463-466

467-474

475-502

Volume ILI. Fune, 1889. Number f.

JOURNAL

OF

NiO OC y.

THE ACTINIARIA OF THE BAHAMA ISLANDS, W.I.
J. PLAYFAIR McMURRICH, M.A., Pu.D.

DurRING the summer of 1887 the Marine Zoological Station of
the Johns Hopkins University was established near Nassau, the
capital of the Bahama Islands, W.L., situated upon the island of
New Providence. Through the courtesy of the Director of the
Station, Dr. W. K. Brooks, I was able to make use of the facili-
ties offered by the Station, and a portion of my stay of five
weeks was occupied in studying the Actinian fauna of the
neighborhood. For the most part, my observations were con-
fined to the vicinity of the Station; but a few excursions were
made to neighboring islands, and on one occasion I visited a
cove situated a couple of miles to the westward of Nassau.

In 1886 the Johns Hopkins Station was located on Green
Turtle Cay, upon the eastern side of Great Abaco Island, one
of the islands of the Little Bahama Bank, lying some hundred
miles to the north of New Providence. While there, the artist,
Mr. Uhthoff, who accompanied the expedition of that year, made
colored sketches in oils of the commoner Actinia collected.
These drawings Dr. Brooks kindly handed over to me, and
though wanting sufficient attention to details, nevertheless allow
of ready identification by one acquainted with the living speci-
mens. The chief value of the drawings lies in their demonstra-
tion of the similarity of the forms inhabiting the Little Bahama
Bank to those found farther south, all the species represented,
with one exception, having been found at New Providence.

2 MCMURRICH. [VoL. III.

All the forms collected were littoral in their habitat. Owing
to the want of the proper facilities I was unable to do any
dredging in deep water.

A few remarks upon the methods of preserving Actiniz are
necessary. The object of my visit to New Providence being
partly to obtain material for class work and specimens for use
in the illustration of my lectures, I was unable to devote as
much time as could be wished to the study of the living speci-
mens of Actiniz. All that I was able to do was to make
careful colored sketches of the various forms collected. The
preservation of Actiniz in a suitable condition for future study
is a matter of some difficulty, and has greatly hindered a thorough
study of the group. The great difficulty experienced in killing
the animals sufficiently rapidly to prevent contraction is the main
obstacle, and the method of first producing torpor by the use
of chloroform or nicotine, as practised by the Hertwigs (’79), is
tedious and not always successful. I was in hopes that good
results might be obtained by the use of cocaine, but my experi-
ments with it gave negative results. The success of any method
depends greatly on the character of the form under treatment.
Methods which will give good results with the Zoanthidz, for
instance, will yield failure quite as often as success with more
contractile forms. . For a collector who cannot give the time
required for the proper carrying on of the narcotizing methods,
my experience has led me to advise the following method of
procedure. After the general characteristics —the coloration,
presence or absence of tubercles, the dimensions, and such
easily observable features — have been carefully noted with as
much detail as possible, the animal is placed in a jar just wide
enough to allow its complete expansion, and with just enough
water to cover it when fully expanded. When this condition is
reached, a glass syringe is filled with Perenyi’s fluid, and this
is suddenly and rapidly injected into the interior of the animal,
the nozzle of the syringe having been quickly inserted into its
mouth. At the same time, if possible, a quantity of the same
fluid is poured over the animal, so that it is bathed without and
within with a tolerably strong mixture of Perenyi’s fluid. It
is left to the action of the fluid for about half an hour, and is
then to be treated successively with 50, 70, and 90 per cent
alcohol, care being taken to inject a considerable quantity of
the spirits into the interior at each change.

No. 1.] ACTINIARIA OF THE BAHAMAS. ie 3

Although considerable contraction usually results from this
process, and although the color is, as a rule, almost destroyed,
yet I think the distortion is less than that resulting from most
other methods, and there is the great advantage that the parts
are preserved in a satisfactory manner for future histological
study. Dissection is possible, owing to the absence of the
excessive brittleness which results from the use of chromic
acid, encrusting or attached calcareous particles are dissolved,
and sectioni=g of entire small forms may be practised without
the danger of ruining the knife, and, lastly, there is no un-
pleasant precipitation of crystals as occurs from the use of
corrosive sublimate when the subsequent washing has not been
sufficiently prolonged.

So far as I am aware, there exist no records of observations
upon the Actiniaria of the Bahamas, although quite a number
of forms have been described from others of the West Indian
islands. Duchassaing and Michelotti (‘60 and ’66) have described
many of the forms occurring in the Antilles; but in their ob-
servations they took account only of external characteristics,
and even with regard to these their descriptions are often so
imperfect as to render it difficult to ascertain the true relation-
ships of the forms under consideration. Lesueur (17) has also
described several forms from the Antilles ; and, lastly, Ellis has
mentioned and figured one or two specimens in a letter to the
Earl of Hillsborough published in the Philosophical Transac-
tions (67).

Owing to the great confusion which exists in the synonomy
and classification of the Actiniaria, notwithstanding Andres’
excellent work (83), it will be necessary to map out the exact
limitations of the various groups and forms to be described
here ; and in most cases an historical review of the synonomy
will be required.

Before concluding these introductory remarks I must ac-
knowledge the obligation under which I rest to the officers of
the Academy of Natural Sciences of Philadelphia, through
whose courtesy and kindness I was permitted to make use of
the magnificent library of that institution. Without this favor
I should have been unable to unravel many of the tangled
threads of synonomy which the investigations to be discussed
in the following pages brought to my notice.

4 McMURRICH. (VoL. III.

ACTINIARIA.
Tribe Hexactini#, Hertwig.

Actiniaria, with paired mesenteries, those of each pair pro-
vided with longitudinal muscle fibres on the faces turned towards
each other, and transverse fibres on the faces turned away from
each other, — except in the case of two pairs, the directives, in
which the arrangement is reversed, the longitudinal muscle
fibres being upon the outer surfaces, and the transverse fibres
on the inner. The number of the pairs of mesenteries present
is at least six, and they increase in multiples of six,

Sub-tribe ACTININZE
= Family Actinine, Andres.

Hexactiniz, with simple uniform tentacles, situated towards
the periphery of the disc, so as to leave the central portion bare ;
each tentacle corresponds to an intraseptal space, and they are
arranged in cycles, and not in radial series.

Family Sagartide, Hert.

Actininz, adhering to foreign bodies by a flat, contractile
base. Column smooth, or provided with verrucz or tubercles,
and perforated by cinclides. Sphincter muscle usually well
developed and imbedded in the mesoglcea,! occasionally absent
or very feebly developed (Aiptasia). The mesenteries of the
first cycle alone are perfect, and are not gonophoric, the repro-
ductive organs being borne by the mesenteries of the second
and third cycles. The free edges of all the septa with mesen-
terial filaments bear acontia. The tentacles are smooth, cylin-
drical, entacmzeous, and are arranged in regular cycles.

The definition of the family Sagartidz given above is essen-
tially identical with that of R. Hertwig (82), the only difference

1 Being convinced that the supporting layer of the Actiniaria cannot be con-
sidered homologous with the mesoderm of the higher forms, I have adopted for its
designation the term mesoglocea proposed by Bourne (Quart. Fourn. Micr. Sci.,N.S.,
Vol. XXVII., 1887).

No:.1./] ACTINIARIA OF THE BAHAMAS. 5

being that I exclude the genus Bunodes which Hertwig includes
in it, on the ground that since one of the forms originally in-
cluded in that genus by Gosse — B. coronata — possesses acontia,
there is a possibility that all the members of the genus may
possess them, though as yet they have not been observed. The
truth of the matter is that the So-called Bunxodes with acontia
described by Gosse (60) and Hertwig really are Sagartidz, the
former belonging, as Andres has pointed out, to the genus
Chitonactts of Fischer (75), while the latter is a Cy/zsta. The
external character, the possession of warts arranged in parallel
rows, is of small importance compared with the internal struc-
tural characters, which in the true Bunodidz are very different
from what is to be found in the Sagartidz. In his later paper
(88), Hertwig corrects the mistake he made in considering his
Cylista minuta a Bunodes.

Gosse’s family, Sagartidze, is slightly different in the forms
included, the difference being due partly to ignorance regarding
the structure of non-British forms, and partly to the attributing
of too much importance to external characters. Dzéscosoma,
which he assigns to this family, belongs really to an entirely
different sub-tribe, and Azptasza, which he places among the
Antheadz, ought to be included. The sub-family Sagartinz of
Verrill (68) and Klunzinger (’77), and the Sagartidz of Andres
(83), differ from the group as I have defined it above by the
exclusion of Phe//za and allied genera on account of their pos-
session of an external investment. It seems hardly correct,
however, to make of the Pe//a forms a group equivalent to the
Bunodidez, for instance ; I should prefer an arrangement of this
kind, —

Family Sagartidz.

(The definition as above.)

Sub-family Sagartine.
Sagartida, without any external membranous investment.

Sub-family Phellinze.
Sagartidz, with an external membranous investment.

6 McMURRICH. [Vot. III.

Genus AIPTASIA, Gosse.

Synon. — Actinia (pars) — Auct.
Cribrina (pars) — Schmarda.
Dysactis (pars) — Milne-Edwards, 1857.
Aiptasia — Gosse, 1860.
Paranthea — Verrill, 1866.
Bartholomea — Duchassaing and Michelotti, 1866.
Sagartia (pars) — Jourdan, 1880.

Sagartidz, with cinclides arranged in from one to several
horizontal rows around the middle of the column. No verrucz.
Sphincter muscle either absent or very feebly developed.
Tentacles strongly entacmzeous.

This genus was established by Gosse for A. Couchiz, and
includes forms which have been variously assigned to the
genera Sagartia, Actinia, Anthea, etc. In fact, not a little con-
fusion exists with regard to the genus. Milne-Edwards (’57)
established the genus Dysactzs, which he referred to his section
of ‘ Actinines vulgaires,”’ forms with a smooth surface, and un-
perforated walls, the distinguishing characteristics of the genus
being the absence of verrucze and of “tubercules calicinaux,”
and the possession of entacmzeous tentacles arranged in two
cycles. The absence of cinclides and acontia would incline one
to deny any similarity between this genus and Gosse’s Azftasza,
but, since two at least of the four original species of Dysactis
are now known to possess these structures, we must consider
the imperfect knowledge of the forms the cause of the erroneous
association of species found in the genus. It is to be noticed
in this connection that the form which Verrill in his earliest
paper (64) refers to the genus Dysactis is, as I have satisfied
myself by the examination of specimens, really an Azptasia —
A. pallida. Subsequently (66), Verrill made this form the
type of a new genus Paranthea.

The genus Dysactis must be considered synonymous in part
with Gosse’s Azftasia, but on account of the imperfection of
the definition, it seems preferable to disregard its priority and
to retain the latter name. As stated above, Gosse (’60), though
recognizing the presence of cinclides and acontia, separated his

1 In neither of the species described here is there any trace of a circular muscle,
and the same is the case with 4. diaphana, according to the Hertwigs (’79). I have
found, however, in 4. pallida a slightly developed muscle imbedded in the mesoglcea.

No. 1.] ACTINIARIA OF THE BAHAMAS. 7

genus from the family Sagartidz to which it properly belongs,
and, making the inability to retract the tentacles of too great
importance, placed it with the Antheadz.

Duchassaing and Michelotti (66), apparently overlooking
Gosse’s Azptasia, established a new genus Bartholomea, whose
definition differs from the original description of Azptasza only
in that the position of the cinclides towards the equator of
the column is particularly mentioned, the genus being thus
separated from Adamsza on the one hand, and WMemactis on the
other. Milne-Edwards’ genus Dysactzs is also retained by these
authors, the form referred to it being probably an Azpfasia
whose cinclides were not very distinct.

1. Atptasta annulata (Les.), And. (PI.1., Fig. 1; Pl. IIL, Fig. 1.)

Synon. — Actinia annulata, n.s. — Lesueur, 1817.
Dysactis annulata— Milne-Edwards, 1857.
Aiptasia annulata— Andres, 1883.
Actinia solifera, n.s. — Lesueur, 1817.
Paractis solifera (Actinia) — Duchassaing and Michelotti, 1860.
Bartholomea solifera— Duchassaing and Michelotti, 1866.
Aiptasia solifera— Andres, 1883.

My reasons for uniting the two genera described by Lesueur
(17) will be more suitably discussed after the form which I
studied has been described.

My specimens were found attached to the lower surface of
the blocks of coral rock, or in cavities in these, along the shore
of New Providence. Among the forms figured by Mr. Uhtoff
I notice one which is evidently A. aznulata, and Lesueur’s
specimen was obtained in the hollows formed in the madrepore
rocks upon the shores of the island of Barbadoes. The form
known as A. solifera was found by Lesueur and Duchassaing
and Michelotti at Guadaloupe and St. Thomas, according to
Lesueur, in old shells, particularly those of Zurbo versicolor (?).
This species consequently ranges from the Little Bahama Bank
as far south, at any rate, as Barbadoes.

The coloration of all my forms was constant (PI. I. Fig. 1).
The column is for the most part pure white, shading off above
into a pale brown, being in this darker region flecked with
opaque white. The cinclidal tubercles are usually more trans-
parent than the surrounding surface, and therefore are quite
evident. The disc is brown, with white triangular spots at the

8 McMURRICH. [VoL. III.

bases of the tentacles of the two inner cycles, towards which
irregular white markings radiate from the white peristome. The
tentacles are brown, ringed with connivent white bands.

The base is adherent and slightly larger than the column,
and is sufficiently thin to allow the attachment of the mesen-
teries to shine through, giving rise to an appearance of white
lines radiating from the centre to the periphery. In preserved
specimens the base is always larger than the column, there being
usually a strong constriction immediately above it. The limbus
is usually more or less crenate.

The column is cylindrical and exceedingly extensible. When
fully extended it measures about 3.6 cm. (according to Lesueur
5-7.5 cm.), with a diameter of 1.8 cm. About midway between
the limbus and the margin it is provided with a series of cin-
clides. Occasionally these are situated somewhat above the
middle, and occasionally slightly below it, but never so low as
to resemble the genus Adamsia. The arrangement of the cin-
clides, which open on tubercles very evident in preserved speci-
mens, is somewhat irregular. They are arranged in vertical
series situated at regular intervals, but the number in each
series varies. Occasionally each series consists of a pair, only
one being placed immediately below the other, or the lower one
may be slightly to the side, so as to appear almost as if alternate.
Quite frequently three cinclides are to be found in each series,
and in one form I counted as many as twelve in some of the
series, the number in all of them being over three. This ir-
regularity is prevalent throughout all the forms I have exam-
ined, and a definite statement as to the number of horizontal
rows in which the tubercles are arranged is impossible, since
not only does the number in the various vertical series vary in
different specimens, but even in the same individual while there
may be six tubercles in one series, in the next there may be
only one, and so on.

The acontia are not emitted with as much readiness as in
some other species of Azpfasza, and it is probably on this account
that Lesueur failed to perceive and record their presence. I
have seen them as white filaments protruded in considerable
numbers through the cinclides.

In none of the specimens that I examined were any signs of
a sphincter muscle observed. It is noteworthy that in one

No. I.] ACTINIARIA OF THE BAHAMAS. 9

specimen there was apparently a total absence of “ yellow-cells ”
in the endodermal epithelium, while in others they were abun-
dantly present.

The tentacles are decidedly entacmzeous and very long, the
inner ones measuring 3.4 cm. in length. In all the specimens
examined they were arranged octamerously in five cycles, the
formula being 8, 8, 16, 32, 64. Lesueur states that the “centre
tentacula are about 6 or 8 in number,” and gives their length as
somewhat greater than those I measured; z.¢., two or three inches.
Whether the words quoted mean that the numbers given were
simply approximate, or that in some forms the arrangement of
the tentacles was hexamerous and in others octamerous, it is
impossible to say; in no case have I observed the hexamerous
arrangement. One of the most striking peculiarities of the
species is the occurrence upon the tentacles of a number of
elevated bands, one above the other, each extending only partly
round the tentacle, the successive bands being connivent. They
are usually of a different color from the rest of the tentacle, and
in preserved specimens stand out very prominently. In trans-
verse sections they are seen to be due to thickening of the
ectoderm, the mesogloea not participating in their formation.
In the thickening are numbers of nematocysts, while elsewhere
these are few in number and apparently smaller, or else absent.
The ectodermal muscular layer of the tentacles is not markedly
developed, presenting no foldings in fully extended tentacles,
and no traces of muscle cells enclosed in the mesogloea. On
account of the absence of a circular muscle the tentacles are
not infolded during contraction.

The septa of the forms examined were in four cycles, the
formula being 8, 8, 16, 32, and only those of the first cycle were
perfect. A large mesenterial stoma is plainly visible on a level
with the cinclides,—the outer one,— while the inner one is
considerably smaller, but still quite evident. The Hertwigs
(79) state that in A. dzaphana the inner stoma is the only one
present, a statement which needs revision. There can be no
question as to the existence of both the inner and the outer
stoma in A. annulata, the size of the latter rendering all doubts
as to its existence impossible.

The longitudinal muscle bands are well developed, and in the
primary mesenteries (Pl. III, Fig. 1) occupy about 4 of the

IO MCMURRICH. {Vot. III.

width of the mesentery. Towards the point of its insertion
into the mesogloea of the column, that of the mesentery is some-
what swollen and presents pinnately arranged rather short stout
processes, those on one side belonging to the longitudinal muscle
system, and those on the other to the parieto-basilar. Internally
to this swelling the mesogloea becomes thinner and then begins
to show on one surface only the muscular elevation belonging
to the longitudinal system. These, at first small, lengthen
gradually as they are traced outwards towards the inner edge
of the mesentery until the largest is reached, when they sud-
denly diminish, the muscle band internally having a rounded
edge, while externally it slopes towards the general surface of
the mesogloea. The parieto-basilar muscle is by no means strong.

None of the forms examined, all of which were collected in
July, have mature reproductive organs. Immature ova are to
be seen, however, partly imbedded in the mesogloea and partly
still forming elements of the endoderm layer. These occurred
only in the mesenteries of the 2d and 3d cycles.

The species described in the preceding pages seems to agree
very well with Lesueur’s description of Actinza annulata (17),
and I have little doubt as to its identity with that form. Du-
chassaing and Michelotti do not, however, record it among the
forms obtained by them in the West Indies, but, on the other
hand, have described a form which they identify with Lesueur’s
Actinia solifera, referring it in their earlier paper (60) to the
genus Paractis, and in the later one to the genus novum Bar-
tholomea ('66), which is identical with Gosse’s Azpfasza. It
seems probable that A. solifera and A. annulata are identical,
the differences being apparently mainly in coloration. The
characters of A. solifera as deduced from the various descrip-.
tions may be given as follows :—Column cylindrical, elongated,
very contractile, marked with longitudinal striz of a reddish
color, and provided with 2-3 rows of small cinclides from which
acontia are emitted when the animal is handled. The disc is
flat, and the peristome white, with two yellow bands opposite
each other (at the gonidial angles, no doubt). The tentacles
are very long, decidedly entacmzeous, in five or six cycles, and
of a brown color annulated with white bands arranged in a
broken spiral. When fully expanded the animal measures about
2 cm. in diameter and 10 cm. in length.

Noor. | ACTINIARIA OF THE BAHAMAS. it

The striation of the column is a comparatively unimportant
character, since Aiptasias which usually present it have been
frequently found without it, or at all events with it so faintly
developed as to be hardly discernible, and in forms so extensible
as this the size is not a character of sufficient importance to
warrant a separation of species. It is possible that Duchassaing
and Michelotti’s A. solifera is really identical with Lesueur’s
annulata, his solifera being really distinct, but it has seemed
advisable to unite the two forms and to retain Lesueur’s specific
name aznulata as indicating a very evident characteristic.

The octameral arrangement of the tentacles and mesenteries
in A. annulata brings up a question as to the validity of Hert-
wig’s tribe Paractiniz, which was founded (’82) upon single
specimens, belonging to two different families, dredged by the
“Challenger” from a depth of 1600 and 2160 fathoms respec-
tively. The tribe is characterized by the number of the anti-
meres not being a multiple of six; in all other respects the two
forms which belong to it resemble Hexactiniz. In one of them,
Sicyonis crassa, the tentacles and mesenterial pairs are 64 in
number; 16 of the pairs of mesenteries are muscular and per-
fect, 16 muscular and imperfect, and 32 small, only slightly
muscular and gonophoric; their formula being evidently 8, 8,
16, 32. Though presenting characters which warrant the for-
mation of a new genus for its reception, yet the number of
mesenteries may possibly be abnormal, and the discovery of
other specimens show that the hexamerous arrangement is the
normal one. There can be no doubt but that the form described
here is Azptasta annulata and belongs to the genus to which it
is assigned, and this fact lends strong support to the idea that
the octamerous arrangement of Szcyonzs is of much less impor-
tance than Hertwig supposed. The other Paractinian, Polyopis
striata, possesses thirty-six antimeres, there being thirty-six
stomidia representing the tentacles and eighteen pairs of mesen-
teries. Hertwig thinks it is ‘most probable that we have here
a tetramerous (octamerous ?) arrangement of the septa, but that
a pair of septa too many has been formed in one interspace on
either side.” It seems however quite as probable, or even more
so, that the arrangement is really hexamerous, only half the
mesenterial pairs of the last cycle being developed. Hertwig
states that “no arrangement into cycles of unequal values could

12 MCMURRICH. [VoL. III.

be made out,” and perhaps the arrangement may be represented
by the formula 6, 6, 4 (12). It would seem at all events that
further observations are needed to authorize the establishment
of the tribe Paractinie.

2. A. tagetes (Duch. and Mich.), Andr.

Synon. — Bartholomea tagetes, n.sp. — Duchassaing and Michelotti, 1866.
Aiptasia tagetes — Andres, 1883.

The forms which I refer to Duchassaing and Michelotti’s
Aiptasia tagetes present considerable variation, and I am some-
what doubtful of the propriety of the identification. The vari-
ous forms of Azptasza resemble each other rather closely, and
it seems to be a question if several of the described species are
not to be considered merely varieties of one widely distributed
species. One of the varieties I include under A. ¢agetes was
found only on one occasion, and then in considerable numbers,
on a sponge, and these I shall first describe, and then consider
a second variety, found upon the under surface of the stones
along the shore, and finally refer briefly to a small, evidently
young, form found in large numbers in a salt lake celebrated for
its brilliant phosphorescence, and situated on the property, on
the island of New Providence, known as “‘ Waterloo.” It is a
shallow lake, bounded at one end by a small mangrove swamp,
and connected with the ocean by a narrow channel about a
hundred yards in length.

Var. a. Spongicola. — Under this designation I shall describe
the form found in the sponge. The column measures about
2.5 cm. in length, and in diameter 0.8 cm. ; in a preserved speci-
men these measurements were respectively 0.7 cm. and 0.6 cm.
In color (Pl. I., Fig. 2) the column is pale brownish white, rather
darker towards the limbus, and near the margin becoming quite
a decided brown marked with opaque white flecks. The disc
and tentacles are brown, also flecked irregularly with opaque
white, and the peristome and stomodzum are white.

The base is firmly adherent, larger than the column, and suf-
ficiently thin to allow the insertions of the mesenteries to show
through. The limbus is very slightly crenate.

The column is cylindrical, tapering slightly towards the top,
and provided with a partly double band of cinclides situated on

WG. F.] ACTINIARIA OF THE BAHAMAS. 13

tubercles, and quite evident. As in A. annulata there is con-
siderable irregularity in the arrangement of the cinclides. The
wall of the column in some of the preserved specimens is suffi-
ciently thin to allow the insertion of the mesenteries to be seen
through it, and I was able accordingly to study the relation of
the cinclides to the mesenteries. In one form examined, the
arrangement was as follows. Starting with an interspace in
which there were two cinclidal tubercles, five spaces destitute
of pores followed, the sixth having only one pore; the fourth
intérspace from this had again only one; the sixth from this,
again one; the eighth from this, one; the fourth from this,
one; the fourth from this, two; and so on. The arrangement
can be better understood from the following scheme :—
i
| | |
|

|

Ten series of cinclides were thus present in this specimen,
there being for the most part a single pore in each series, only
two interspaces possessing two pores. As a rule, a series is
situated on each fourth interspace, but there are three excep-
tions to this: in two cases the series is on the sixth interspace
from the one preceding it, and in the third case it is on the
eighth, this being probably the result of a series having been
omitted. In another specimen I could distinguish only nine
cinclidal series, and of these only one or perhaps two consisted
of two pores. The relation of the pores to the septa could be
made out only for a few series, the arrangement for these being,

WA
MH
Here again between the first and second series one has probably
been omitted. In a third specimen I could count only eight
series of cinclides, and in this the number of interspaces was
in one case eight, in four cases four. In none of the specimens
were there twelve cinclidal series, though the numbers given
for the last two forms should probably be larger, some of the

pores having been no doubt hidden by the contraction and
wrinkling of the column wall.

I

OF ON Or) ||||O ie)
|

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1
y
!

Oo
12)

12) Oj} ||O]|||O

O}

14 MCMURRICH. [Vot. III.

Acontia were observed protruding at the cinclides, at the tips
of the tentacles, at the limbus, and even through the base.
They were always white.

No sphincter muscle is present. ‘Yellow cells” are abun-
dant in the endoderm of all the specimens examined.

The tentacles are strongly entacmzous, the length of those
of the inner cycle being 0.9 cm., and of those of the outer cycle
0.15 cm. They are arranged in five cycles, their formula being
6, 6, 12, 24, 48, although this arrangement was somewhat
obscured by the members of the first two cycles appearing to
form only one containing twelve tentacles. The mesogloea of
the tentacles, as of the other portions of the body, is thin, and
this is characteristic of all the species of this genus that I have
studied. The muscles of the tentacles are simple and only
slightly developed. On account of the absence of a circular
muscle the tentacles are not infolded in contraction.

The mesenteries are in four cycles arranged thus (Pl. III,
Fig. 3): those of the first cycle (I.) only are complete, those
of the second (II.) are large and well developed, those of the
third (III.) quite small and apparently without mesenterial fila-
ments, and those of the fourth (IV.) are minute processes of
the mesoglcea of the column which do not project beyond the
surface of the endoderm. The formula of the mesenteries is
6, 6, 12, 24. The number of the stomata present was not made
out with certainty, but there appeared to be two, situated as in
A. annulata, an outer and an inner one. The longitudinal
muscle bands are developed in the mesenteries of the first and
second cycles; they occupy a considerable portion of the surface
of the mesenteries, their elevation gradually diminishing towards
the inner edge. The bases of all the mesenteries are dilated
somewhat, but in those of the first and second cycle there is no
pinnation of the dilated portion, while in the small and poorly
developed mesenteries of the third cycle it was present. The
parieto-basilar muscle is very weak. The reproductive organs
were confined to the mesenteries of the second cycle. All the
specimens examined were males with mature or nearly mature
spermatozoa.

Var. 8. Castanea.— This variety was found not very abun-
dantly upon the under surface of blocks and fragments of coral
rock along the shores. The color of the column is pale reddish

No. 1.] ACTINIARIA OF THE BAHAMAS. I5

brown, with lighter longitudinal striz marking the lines of in-
sertion of the mesenteries. The disc and tentacles are brown,
flecked with opaque white patches. The peristome and stomo-
dzum are white, or in some cases the peristome is brown,
slightly paler than the disc, and flecked with white spots.

The base adheres firmly, and is slightly larger than the col-
umn, measuring about I.4 cm. in diameter. It is thin enough
to allow the insertions of the mesenteries to be seen through.

The column is cylindrical and contractile, measuring about
1.5 cm. in height and 0.gcm. in diameter. The cinclides are not
very distinct in the living animal, although in preserved speci-
mens they stand out as tubercles quite as distinctly as in the
other variety, being arranged very much in the same manner
as in it. In one specimen the numbers in the various series, as
faniasseculelbe made out ran’: thug 3) ty.T). lyi2) Ey 2p By Ze 1, ¥.
Acontia were emitted with comparative readiness, and were
always white. There is no sphincter muscle, and the endoderm
contains “yellow cells.”

The tentacles are very entacmzous, and are arranged in four
cycles, their formula being 12, 12, 24, 48. The length of those
of the inner cycle is 1.2 cm., and of those of the outer cycle
0.75 cm. As in variety a, they are all smooth, cylindrical, and
pointed, and on account of the absence of a circular muscle are
not infolded in contraction.

The description given of the arrangement of the mesenteries
of variety a applies equally well for this variety, the only differ-
ence being that the internal edge of the longitudinal muscle
bands ends more abruptly (Pl. III., Fig. 2). I did not succeed
in observing the stomata.

Reproductive organs are present only on the mesenteries of
the second cycle. In the specimens examined only ova were
present, and they were not quite mature.

Young Form.— This was obtained in considerable numbers
on the grass along the shores of the lake mentioned above, and
I was at first inclined to consider it a distinct species; but
further study has led me to place it here as a young form of
A. tagetes. In coloration it agrees closely with variety £, just
described, the column being brown with longitudinal striae indi-
cating the insertion of the mesenteries. Above the color be-
comes deeper, and in this darker region the column is flecked

16 McMURRICH. [Vot. III.

with opaque white. The tentacles and disc are brown, also
flecked with opaque white; and the peristome is white.

The base is firmly adherent and somewhat larger than’ the
column. The latter measures from 0.5-I cm. in height and from
0.3-0.4 cm. in diameter, and is provided with a single row of cin-
clides situated on tubercles, and six in number. They are color-
less and transparent, so that they are quite conspicuous. No
trace of a sphincter muscle could be seen ; and as in the forms
already described, the “yellow cells’’ were abundant in the
endoderm.

The tentacles are entacmzeous, and in four cycles, their
formula being 6, 6, 12, 24. The length of those of the inner
cycle is about 0.4 cm.

The mesenteries are arranged in three cycles. Of these, the
first is perfect ; the second, imperfect and small, and not provided
with mesenterial filaments; while the third is represented by
the merest rudiments of processes from the mesogloea of the
column wall. In one specimen examined there was a difference
in the mesenteries of the two halves of the body. In one half
there were three perfect pairs of mesenteries, and in the other,
four, the secondary and tertiary cycles being arranged corre-
spondingly. I could not discover the mesenterial stomata, nor
a parieto-basilar muscle. The longitudinal muscle bands of the
perfect mesenteries cover only a comparatively small portion of
the surface of the mesentery, and end abruptly internally, as in
variety £.

In none of the specimens examined were there any traces of
reproductive organs, as might be expected from the slight devel-
opment of the mesenteries of the second and third cycles.

My reasons for at first supposing this form to be a distinct
species were its occurrence in such large numbers, all being
about the same size, and the failure to obtain any larger speci-
mens, resembling varieties a or 8, from the lake. A careful
examination of the shores and deeper portions of the lake was
not made; and it is probable that adult specimens of variety B
may be found there, in the deeper water, a little way out from
the shore, the shallower water and the grass abounding there,
with the myriads of copepods swimming about among it, afford-
ing more suitable conditions for the growth of the young forms.
There can be no doubt but that the specimens are young, and

No. 1.] ACTINIARIA OF THE BAHAMAS. 17

the similarity of coloration inclines me to the belief that they
belong to variety £.

- Duchassaing and Michelotti state that A. tagetes is character-
ized by the presence of a double row of cinclides, indications of
a third imperfect row being usually present. It differs in this
respect from the form I have just described ; but it also fails to
agree with the figure they give of the species (66, Pl. VI., Fig.
16), which is represented with a perfect row above, and below this
a second imperfect row. The Azptasza (Lartholomea) tinula of
the same authors is said to have only a single row, and in this
perhaps agrees more nearly with my specimens; but I do not
consider that an identification with that form would be as
satisfactory as that employed.

The species was originally described from specimens obtained
at Porto Rico and St. Thomas, and probably ranges throughout
the West Indies. It seems to be rather closely related to the
A. pallida of the Eastern coast of North America, and may
prove to be identical with it, and also bears considerable resem-
blance to A. saxicola, judging from Andres’ description of that
form (83).

Family Antheade, Hert.

Synon. — Actinines vulgaires (pars) — Milne-Edwards, 1857.
Actiniadze — Gosse, 1858.
Actiniade (pars) + Antheadz (pars) — Gosse, 1860.
Actininz (pars) — Verrill, 1868.
Antheade — R. Hertwig, 1882.
Actinidz + Cereactida — Andres, 1883.

Actininz: adhering to foreign bodies by a flat contractile
base. Column usually smooth, occasionally verrucose towards
the upper part, without cinclides. Margin frequently provided
with acrorhagi, but may be smooth. Tentacles numerous, long,
cylindrical, and smooth. Sphincter muscle only slightly devel-
oped, diffuse. Perfect mesenteries numerous, and all, except
the directives, gonophoric. No acontia.

The synonomy of this family as defined above is somewhat
complicated. Milne-Edwards’ division of Actinines vulgaires
(57) contains certain forms (¢¢., Paractis, Corynactis) which
must be referred to other families, and is consequently not quite
comparable to the Antheadze as limited above. Gosse’s family,

18 MCMURRICH. (Vou. III.

Actiniade, however, agrees closely; but in his larger work (’60)
he separated it into two families, —the Antheade, characterized
by possessing no acrorhagi, and the Actiniadz, which did possess
them. Of the forms which he included under the former family,
Azptasia has already been shown to be a Sagartid; Axthea (A.
cereus) has been shown to possess acrorhagi, which are not,
however, conspicuously colored; the Actznza pustulata of Dana
is a Phymactis; and Actinopsis has been referred by Andres
(83) to an entirely different family. The three genera referred
to the Actinidz suffer a similar dispersion, the genus Actinza
being the only one which truly belongs to the family. Verrill
in his earlier papers adopted Gosse’s arrangement, but subse-
quently united the two families under the term Actinine, includ-
ing, however, certain forms which should certainly be separated.
Andres likewise unites Anthea and Actinia in one family, but
established another, Cereactide, for a form not possessing
acrorhagi. This I do not consider necessary, since, as will be
shown, the internal structure of the members of the genus
Cereactis (Condylactis) is similar to that of the Antheas and Ac-
tinias so far as is known.

Gosse’s original name, Actiniadz, would perhaps be preferable
to that employed, since the generic term Azthea ought appar-
ently to be replaced by Amemonia, which has the priority. On
account of its similarity, however, to the term employed to
designate the sub-tribe, but especially since Antheadz has
already been used by R. Hertwig (82) with the same limitations
as are applied to it here, I have thought it well to retain the
latter name.

Genus Conpytactis, Duch. and Mich.

Synon. — Actinia (pars) — Auct.
Condylactis — Duchassaing and Michelotti, 1866.
Cereactis — Andres, 1883.
Antheade, with the column smooth or slightly verrucose
towards the upper part. Margin elevated slightly, so as to
form a collar; not provided with acrorhagi.

3. Condylactis passifiora, Duch. and Mich. (Pl. 1, Fig. 3;
Pl. III., Figs. 4-6.)

This is one of the most abundant and striking forms obtained.
It was found in considerable numbers on the under surface of

No. I.] ACTINIARIA OF THE BAHAMAS. 19

overhanging ledges, or in depressions or cavities in the coral
rock; it is also one of the forms figured by Uhthoff as occurring
at Green Turtle Cay. It seems tolerably certain that the form
described by Duchassaing and Michellotti from St. Thomas as
Condylactts passifiora is identical with the Bahaman form under
consideration. The description given by those authors, how-
ever, is far from perfect, and presents certain differences from
what I find in the Bahama specimens, which are, however, I
think, capable of explanation. A discussion of this point will,
however, be deferred until a description of the specimens stud-
ied has been given. I would merely point out here that Andres’
generic term Cereactis must be replaced by Condylactis, which
has the priority.

The column is usually bright scarlet in color, becoming some-
what brownish above; the disc is pale brown, and the tentacles
are of the same shade, usually tipped with crimson, and assuming
when contracted a somewhat greenish hue. In some cases the
crimson tips are wanting. The color of the column varies
somewhat ; occasionally it is somewhat darker, more brownish,
' than in the specimen figured; in other cases the coloring matter
is arranged in closely approximated minute dots, and in others,
again, it is uniformly distributed, but much paler, varying to
orange, or even yellow.

The base is firmly adherent and somewhat larger than the
column. The limbus is crenated. The column varies considerably
in the amount of extension, the same individual measuring, when
fully extended, about 11 cm. in length and 3.75 cm. in diameter ;
while when in the condition which may be termed expansion it
measures only 7 cm. in height by 6.3 cm. in breadth. In the
preserved specimens the height is about 4 cm. and the diameter
5.5 cm. In adults the column is apparently smooth, but in
smaller individuals it is furnished in its upper part with small,
irregularly scattered verrucz, which, however, do not seem to
be as adhesive as they are in C. aurantiaca, according to Andres.
The sphincter muscle is only very slightly developed, and is of
the diffuse type (PI. III., Fig. 4), and, consequently, the infold-
ing of the tentacles during contraction is by no means perfect.
The mesogloea of the column wall is comparatively thick, meas-
uring about 0.17 mm. The endoderm is richly supplied with
“yellow cells.”

20 McMURRICH. Vor. Iii:

The margin is crenate, the indentations corresponding to the
insertions of the mesenteries. It is somewhat elevated, so as
to form a slight collar, separated by a naked area from the ten-
tacles. These are smooth, cylindrical, and only slightly entac-
mzous. They are 96 in number, and are arranged according
to the formula, 6, 6, 12, 24, 48, although they appear to be in
four cycles only. Pores are present at their extremities, as was
shown by the jets of water which issued therefrom when the
animal was induced to contract suddenly, but I was unable to
demonstrate any openings in my sections. The ectodermal
muscles are arranged on well-marked elevations of the mesogloea
(Pl. III., Fig. 5), which occasionally, but not very frequently,
anastomose, thus enclosing a number of muscle-cells within the
mesogloea. The disc is concave and smooth, and considerably
broader than the column, measuring in the extended condition
II cm. in diameter, and in the expanded condition about 18 cm.
The ectodermal muscles are arranged similarly to those of the
tentacles. The mouth is large, and the peristome not markedly
elevated. The gonidia are large and prominent, and colored
similarly to the disc.

There are 12 perfect mesenteries, 12 which are attached to
the stomodzum for about half its length, but are free below,
and 24 which are quite imperfect, or united to the stomodzeum
only toa very slight extent. The longitudinal and parieto-basilar
muscles are well developed, a characteristic of the former being
the difference in the length of the various mesogloeal processes,
whereby the bands have a sinuous outline in transverse sections
(Pl. III., Fig. 6). The mesenteries of all the cycles, with the
exception of the directives, are gonophoric. Only the inner
mesenterial stomata are present.

The points in which Duchassaing and Michelotti’s description
of Condylactis passifiora (’66) differs from the specimens obtained
by me are principally that these authors state that the column
is provided with ‘“tuberculis parvis sparsis: numerosisque,”
and, secondly, they do not describe the tentacles as possessing
crimson tips. As regards this latter point, as stated above, I
obtained some specimens in which this striking coloration of
the tentacles was wanting. The absence of the tubercles seems,
however, more important. In the figure which Duchassaing
and Michelotti give (66, Pl. V., Fig. 7) they are represented as

No. 1.] ACTINIARIA OF THE BAHAMAS. 21

minute points scattered irregularly over the column; and I am
inclined to believe that these authors had to do with a specimen
in which the coloring matter was distributed in minute dots
over the surface of the column, in which case, as I can testify
from experience, the appearance is strongly as if the column
was covered by exceedingly minute scattered tubercles. In
other respects, judging both from the description and from the
figure, the correspondence to the Bahama specimens is so great
as to allow of little doubt of their identity with the St. Thomas
forms.

C. aurantiaca (D. Ch.), the Cereactis aurantiaca of Andres
(83), is certainly closely related to C. passtflora, but differs
sufficiently to constitute another species. The most important -
difference lies in the absence of the verrucz in the adult fassz-
flora; while in aurantiaca, according to Andres, they are very
evident, being of a pure white on a brownish ground, and tolerably
large. A nearer relation is apparently to be found in the Parac-
tzs erythrosoma of Klunzinger ('77), which inhabits the Red
Sea. This form, originally discovered by Ehrenberg (’34), was
referred by him to the genus Actinza (/sacm@a); Klunzinger,
however, transferred it to the genus Paractis on account of its
possession of a margin raised so as to form a collar; and Andres
placed it among the doubtful forms belonging to the genus
Anemonia, regarding it as related to A. sulcata. I have little
doubt but that this form is to be referred to the genus Condy-
factis, and that its correct appellation is C. erythrosoma (Ehr.).
It agrees in many particulars with the Bahama specimens, and
I am almost inclined to consider the two forms identical; but
on account of the absence of any information as to the internal
anatomy of the Red Sea form, I have thought it better to sep-
arate them. In the absence of verrucz, and in the general
coloration, the resemblance is very striking. In some details of
the coloration, however, such as the greenness of the tentacles
and in the size, differences, not very important certainly, are to
be noticed.

If Andres’ description of the genus (founded upon a single

1 Ina preliminary notice of this paper, which was published in the Fokus Hopkins
University Circulars, Vol. VIIL., No. 70,1 referred to this form as Cereactis Bahamen-
sis, n. sp., indicating, however, its probable identity with Condylactis passifiora. I
have since become convinced of the correctness of such an identification.

22 McMURRICH. (VoL. III.

species) be accepted, C. passiflora will be excluded from it.
The presence of verrucz, which Andres makes of so much
importance, cannot, it seems to me, be considered a generic
characteristic, since in the Bahama specimens they are present
in young individuals, but disappear in the adults. Since, then,
the Bahama species agrees so closely in other particulars with
the European form, I have given the definition of the genus so
as to include forms both with and without verruce.

Family Bunodidz, Gosse.

Synon. — Actinines verruqueuses — Milne-Edwards, 1857.
Bunodidz — Gosse, 1860.
Cereze — Duchassaing and Michelotti, 1866.
Bunodine — Verrill, 1868.
Tealidaee— R. Hertwig, 1882.

Actininz adhering to foreign bodies by a flat contractile base.
Column occasionally smooth, but usually provided with tubercles
either simple or compound. No cinclides. Sphincter muscle is
strong and circumscribed. Perfect mesenteries usually numer-
ous, those of the first cycle, with the exception of the directives,
being gonophoric. No acontia. Tentacles smooth, cylindrical,
and entacmzeous.

Gosse, who established this family, Jaid most stress on the
presence of the tubercles, and this has usually been considered
the characteristic of the family, though later authors have added
the character of the absence of acontia, thus excluding from the
family a single species, Bunodes coronata, which was included
by Gosse. The true relationships of this form have already
been referred to. Hertwig’s original objection (’82) to the term
“ Bunodidz”’ is based upon this error of Gosse, and he has since
(88) withdrawn his name Tealidz in favor of the older one.
He was, however, the first to point out the systematic value of
the well-developed circumscribed sphincter muscle, and to make
this and the absence of acontia two important characteristics of
the family, at the same time lessening the excessive importance
of a tuberculated column by including a genus, Lezotea/ia, in
which the column wall is smooth. The presence of a large
number of perfect mesenteries is also an important character-
istic; but in one genus at least, as I shall show, this feature is
wanting.

No. 1.] ACTINIARIA OF THE BAHAMAS. 23

Genus BuNOoDES, Gosse.

Bunodidz with the column provided with tubercles arranged
in vertical series, of which either all reach the limbus, or only
those corresponding to the primary tentacles, in which case the
other series stop at varying distances from the margin according
to their importance. Margin tuberculate, and forming a more
or less distinct collar. Tentacles polycyclic and entacmzous.
Twelve pairs of perfect mesenteries.

The limitations of this genus have already been indicated.

4. Bunodes teniatus,n. sp. (Pl. 1., Fig. 4; Pl. IIL, Fig. 7.)

The single specimen of this species which I obtained was
found on the under surface of a block of coral rock in the bay
to the westward of Nassau. The color of the column is olive
green ; the tubercles with which the column is covered are of
two different colors, arranged so as to form twenty-four longi-
tudinal bands. Twelve of these, each containing five vertical
rows of tubercles, are of the same color as the column, the
other twelve, each containing three vertical rows of tubercles,
being more yellowish. The acrorhagi are also yellowish, while
the tentacles are gray with transverse oval blotches of opaque
white on their inner surfaces. The disc and peristome are olive
green.

The base is strongly adherent and somewhat larger than the
column, which measured about 3.2 cm. in height in the fresh
condition, the diameter being about the same; in preserved
specimens the height is about 1.5 cm. The entire surface of the
column is covered with tubercles disposed in vertical rows, and
placed so closely as to allow the general surface of the column
wall to be seen only with difficulty. There are altogether 96
rows of these tubercles, all of which extend from the margin,
which is provided with acrorhagi, to the limbus, and there is
little, if any, difference in the size of the tubercles in the vari-
ous rows. In structure the tubercles are markedly different
from the verrucz which are to be found in Aw/actznza (see below),
and resemble very closely the acrorhagi. In fact, the figure
given by the Hertwigs (’79) of the acrorhagi of Avzthea cereus
would almost answer for a figure of the tubercles of Bunodes,
except that the nervous layer is not so readily seen in the latter,

24 McCMURRICH. [VoL. III.

and the tubercles project more above the general surface. They
are simply batteries of nematocysts, the presence of these bodies
at once distinguishing them from the verrucze of Az/actinia, etc.

R. Hertwig (82) has stated his objections to the presence or
absence of elevations of the column wall being considered of
systematic importance except in so far as genera and species
are concerned. That these objections must be sustained is
certain; but it also seems probable that more attention ought
to be paid to the structure of the elevations than has hitherto
been done. It is possible to distinguish in them at least three
varieties: (1) simple elevations of the mesogloea unaccompanied
with any extensive modification of the ectodermal epithelium,
e.g. Bunodes gemmacea according to Jourdan (80), and ‘Bunodes
(Cylista) minuta, R. Hertwig (82) ; (2) evaginations of the entire
column wall furnished with numerous nematocysts, as in the
acrorhagi of Awthea, etc., and the tubercles of Bunodes tentatus ;
and (3) verrucz in which the ectoderm consists of peculiar elon-
gated cells, quite different from those of the column wall in
general. Jourdan, in his description of the tubercles of Bunodes
gemmacea, apparently considers them to be produced by the
dipping down of the ectoderm between them into the mesogloea
to form what he terms “verrues glandulaires.” R. Hertwig has,
however, shown by his observations on Lunodes (Cylista) minuta
(82) that Jourdan’s interpretation of the appearance presented
by his sections was erroneous, and has maintained that these
apparent ectodermal enclosures within the mesogloea were pro-
duced by the contraction of the column wall of the specimen
examined, whereby deep pleatings were produced which “may
look like detached epithelial islands in transverse section.”’ This
being the case, the elevations of Bunxodes gemmacea belong to the
first of the three groups enumerated above, and are markedly
different from those of B. ¢enzatus.

The sphincter muscle (Pl. III., Fig. 7) is very strong, forming
a large projection into the body cavity. In transverse section
it has a more or less circular outline, and is attached to the
column wall by a pedicle of mesogloea which has a fenestrated
appearance, containing numerous cavities lined with muscle
cells. From this pedicle the mesogloea processes arise in a very
irregular manner and anastomose in all directions, so that the
central portion of the muscle thickening appears to have a

No. 1.] ACTINIARIA OF THE BAHAMAS. 25

reticular structure, there being here and there areas of mesogloea
of varying size. Towards the exterior the mesogloeal processes
cease to anastomose, and run radially toward the surface of the
thickening. The thickening thus appears to be composed of
two parts passing gradually into each other, a central part of
reticular structure, and a peripheral part composed of mesoglceal
processes arising and radiating out from the reticular portion.
The muscular layer throughout the rest of the column is weak,
and the mesoglceal layer is comparatively thin. The endoderm
throughout contains numbers of “yellow cells” and a dark
pigment which persists in preserved specimens, and is therefore
not soluble in alcohol nor destroyed by weak nitric or chromic
acids.

The margin is furnished with acrorhagi, slightly tuberculate
upon their outer surfaces; they are simply the enlarged upper-
most turbercles. The tentacles are not very long, the inner
ones measuring about I.9cm. They are entacmzous, cylindri-
cal, and arranged in five cycles, their formula being 6, 6, 12, 24,
48, there being thus 96 in all. In cross section the thinness of
the mesogloea and the absence of any muscular processes are
noticeable.

The ectodermal musculature of the disc is not particularly
strong, the mesogloea being raised into processes of no very
great height. There are no enclosures of muscle cells in the
mesoglcea as in 7ealia crassicornis.

There are altogether 48 mesenteries, and of these 24 are
perfect and 24 imperfect ; 12 of the perfect ones, however, are
not attached quite so far down the stomodzeum as the other 12,
to which latter series the directives belong. The longitudinal
and parieto-basilar muscles are present, but show no peculiarities
calling for special mention, except that the former are by no
means so prominent as in TZealia crassicornis or bunodiformis.
All the mesenteries, with the exception of the directives, are
gonophoric. I was not able to discover any mesenterial stomata,
though it appeared as though the inner ones were present.

Before I had concluded my study of this form I felt inclined
to identify it with the European B. gemmacea. The extension
of the geographical area inhabited by that species by such an
identification seemed a much slighter obstacle than certain
structural discrepancies, some of which, however, seem to be in-

26 McMURRICH. [Vot. III.

cluded in the variations which the species presents. For instance,
in B. gemmacea, as figured by Gosse (60) and Andres (’83), the
tubercles do not as a rule all reach the limbus, but only those
of the primary series. In Figure 2 of Gosse’s Plate IV. the
arrangement is similar to what occurs in the Bahama specimen,
so that this difference may be overlooked. Again, in most cases
it is only the primary tubercles which are lighter in color; but
Gosse states that “sometimes, however, the quaternary row
which bounds each primary on each side is also white,” and he
figures such a condition in Pl. IV., Fig. 3. If one imagines a
form with the rows of tubercles all reaching the limbus, and
having not only the primary tubercles, but also the quaternaries
on either side, light colored, —a combination, in fact, of the two
varieties figured by Gosse, — we would have a near approach to
the condition of the Bahama form. But there is still another
difference. In the European Gem there are only six light-colored
bands, whereas in the form I have described these are twelve in
number. This seems a serious discrepancy; but an approach
towards such a condition is to be found in the European forms.
In these the warts of the secondary series are usually some-
what paler than those of the tertiary series, and if the paleness
should become as marked as in the primary series, and have
extended so as to include the series on either side, we should
have the arrangement which is found in the Bahama specimen.
The presence of a fifth series of tubercles, or, in other words,
of 96 series of tubercles, seems to be a more important charac-
ter than that of the coloration. In the European forms appar-
ently the number of series is invariably 48; but whether this is
sufficient for the establishment of a new species seems to me
doubtful. The discrepancies of coloration, too, may be depen-
dent upon the presence of the extra series of tubercles.

Even allowing, however, these possibilities, B. zenzatus must
be considered a decidedly aberrant variety. I have thought it
advisable, however, to consider it a distinct species, particularly
on account of the difference in the structure of the tubercles,
which has been referred to above. The erection of a new
species from the study of a single specimen is usually a dubious
matter, and it is quite possible that the examination of a num-
ber of specimens, and a further study of the histological struc-
ture of the tubercles of B. gemmacea will necessitate the union
of the two forms.

No. I.] ACTINIARIA OF THE BAHAMAS. 27

The form described by Lesueur (17) from St. Vincent as
Actinia bicolor has been assigned by Gosse (’60) to the genus
Bunodes. In coloration it resembles 2B. teniatus, the column
being “divided longitudinally with brown and white bands,”
and the tentacles having “a row of white spots on the superior
part.” In other respects, however, there appear to be decided
differences, and, judging from Lesueur’s description, his A. dzco-
Jor should be assigned to the genus Adamsza, as has been done
by Andres (83). The limbus only is furnished with tubercles,
of which, however, there are several rows; and in habit also it
resembles the members of the genus Adamsza, being found
adhering to shells.

There seems to be a good deal of probability that B. tenzatus
is simply a color variety of Lesueur’s Actinza granulifera (17),
which has been variously referred to the genera Az/actinta,
Oulactis, and Anthopleura. Among the forms figured by Uht-
hoff, from Green Turtle Cay, is one evidently identical with
Lesueur’s species. I did not find any specimens similar to that
from Green Turtle Cay with which to compare my ZB. senzatus,
and accordingly prefer to consider it distinct for the present.
I have no doubt but that Lesueur’s A. granulifera is a Bunodes.

Genus AULACTINIA, Verr.

Synon. — Actinia (pars) —L. Agassiz, Ms., 1849.
Aulactinia — Verrill, 1864.

Bunodide, with the upper portion of the column provided
with longitudinal rows of verrucz, the lower portion being
smooth. The margin forms a more or less distinct collar, and
the tentacles are polycyclic and entacmzous. The six pairs of
mesenteries of the first cycle are alone perfect.

Verrill, who first defined this genus, seems to have placed too
much importance upon the lobation of the upper verrucze, which
were considered acrorhagi, and in this Andres has followed
him. The essential peculiarities of the genus, as it is under-
stood here, are the limitation of the verrucz to the upper part
of the column, and the small number of perfect mesenteries.
This latter characteristic I have found to hold in A. cafitata,
the type species of the genus.

28 MCMURKRICH. [Vou. III.

5. Aulactinia stelloides,n.sp. (Pl. 1, Figs. 5-6; Pl. IIL, Figs.
8-10.)

This form was found usually buried up to the tentacles in the
sand in tidal pools, but also not unfrequently on the under sur-
face of blocks of coral rock along the shore in shallow water.
In color the column (PI. I., Fig. 5) is brown, darkening above,
and pale, and, in some cases, almost colorless below, the lines of
the insertions of the mesenteries being usually evident. The
verrucz, on the upper part of the column, are pale, almost
white. The tentacles are brown, or almost cream-colored, and
are banded or mottled upon their inner surfaces with white,
which sometimes varies to olive-green. Disc (Pl. I, Fig. 6),
olive-green, with a zig-zag band of white about midway between
the bases of the tentacles and the mouth. Ina small specimen
the tentacles were almost white, their mottlings being opaque
white, and in this case the disc also was almost white, with only
a faint indication of green.

The base is rather strongly adherent and somewhat larger
than the column, measuring about 1.3 cm. in diameter. The
column is cylindrical, measuring in the fresh condition 1.7 cm.
in height and 1.1 cm. in diameter; in the largest of the pre-
served specimens these measurements are about 0.8 cm. and
I. cm. respectively. The lower portion is smooth, while the
upper one-third is provided with vertical rows of verrucz, to
which particles of sand, etc., adhere. The upper verrucz are
more prominent than those lower down, the marginal ones
being the largest of all, but showing no indications of lobation.
Structurally the verrucz are elevations of the entire column
wall, the ectoderm, mesogloea, and endoderm being, as it were,
blown out at certain spots to form hemispherical elevations
(Pl. III., Fig. 8). The mesogloea, in the centre of the verruce,
is quite smooth on both surfaces, but around the margin its
endodermal surface is raised into rather strong finger-like pro-
cesses (mp), covering which are the endodermal muscle cells.
The ectoderm of the central portion (mec) is markedly different
from that found at the margins and on the column wall gener-
ally; it is composed apparently altogether of exceedingly fine,
almost filiform cells, there being none of the claviform gland
cells elsewhere abundant, and apparently no “stutzzellen.” It
is difficult to separate these cells from the mesogloea by macera-

No. 1.] ACTINIARIA OF THE BAHAMAS. 29

tion, the ordinary ectoderm cells surrounding them being on the
other hand easily separable, a fact which has been observed by
von Heider (77) as characteristic of the similar cells of the
verruce of Heliactis. The histological structure of verrucz will
be discussed more fully later on under Phymanthus cructfer,
where they are well developed and suitable for investigation.

The sphincter muscle is strong and of the circumscribed type
(Pl. III., Fig. 9). The mesogloeal processes supporting the en-
dodermal muscles become somewhat stronger as they approach
the region of the circular muscle, and then suddenly become
much elongated and branched, forming a ridge almost circular
in cross section, projecting into the body cavity. There is no
distinct pedicle from which the processes take a common origin,
as in other Bunodidz which have been examined, but most of
the processes arise independently from the mesogloea layer,
only those towards the inner part of the thickening arising from
a common lamella, or process, which, however, is thin, and not
at all pedicle-like. ‘Yellow cells” are everywhere abundant in
the endoderm.

The margin is somewhat raised, forming a collar, a bare space
intervening between it and the bases of the outermost tentacles.
It bears the uppermost of the verruce, which, as already stated,
are not lobed and do not present any difference of structure
from those found on the column. The tentacles are cylindrical
and decidedly entacmzeous, the inner ones measuring I.7cm. in
length, and the outer 0.8 cm, They are 48 in number, being
arranged in four cycles, thus: 6, 6, 12, 24.

The mesenteries are arranged in five cycles, only those of
the first cycle being complete (Pl. III., Fig. 10), and of these
the directives are united to the stomodzeum to a greater extent
than the others, the lips of the gonidial grooves being prolonged
downwards to form languettes with which the directives are
united. The mesenteries of the second cycle (II.) are nearly
if not quite as well developed as those of the first cycle, but are
all imperfect ; those of the fourth cycle (IV.) have well-developed
muscle bands, but no mesenterial filaments; while the members
of the fifth cycle (V.) are very diminutive, not projecting be-
yond the surface of the endoderm, and in the specimen exam-
ined, were not present in certain interseptal spaces where they
should have occurred, the cycle being thus incomplete. The

30 MCMURRICH. [VoL. III.

rudimentary nature of this last cycle is also evidenced by the
absence of a fifth cycle of tentacles, there being usually one
cycle of tentacles more than mesenteries. I do not think that
the small size and incompleteness of these mesenteries are due
to the specimens examined being young, but rather imagine
that there is a tendency towards the disappearance of this cycle
in this form.

The inner mesenterial stomata only were observed. The
muscle bundles, both longitudinal and parieto-basilar, are pres-
ent, and fairly well developed. In one specimen examined, one
mesentery of a pair belonging to the first cycle had longitudi-
nal muscle fibres equally well developed upon both its surfaces,
the parieto-basilar being absent, and a greater portion than
usual of the surface of the mesentery was covered with muscle
fibres. The reproductive organs are borne by the mesenteries
of the first and second cycles (Pl. III., Fig. 10), with the excep-
tion of the directives. On some of the mesenteries of the
second cycle they were absent; but no regularity was apparent
in their occurrence or absence on different mesenteries of the
cycle.

This form seems to resemble in some respects Bunodes stella,
Verrill (64), and I regret that my efforts to obtain specimens of
that species for comparison were unsuccessful. Andres ('83)
places it among the “ Bunodidz incerto sedis,” being uncertain
whether to consider it a Bunodes, Phymactis, or Aulactinia.
Perhaps further investigation will demonstrate the identity of
the two forms, in which case they should both be included under
the name Avdlactinia stella.

In placing Az/actinta among the Bunodidz, the importance
of one of the fundamental peculiarities of the family as defined
by R. Hertwig (82), viz., the presence of numerous perfect mes-
enteries, has been lessened. I was at first inclined to separate
Aulactinia from the Bunodidz on account of the small number
of perfect mesenteries which they possess, but further consid-
eration showed the inadvisability of such a classification, since
in other important features, such as the presence of a strong cir-
cumscribed endodermal muscle, of reproductive organs on the
mesenteries of the first cycle, and in the absence of cinclides
and acontia, there is agreement. The small number of perfect
mesenteries does not seem to be a character of sufficient impor-

No. I.] ACTINIARIA OF THE BAHAMAS. 31

tance to warrant the establishment of a new family, since in the
Bunodidze which have been examined there is considerable vari-
ation in the number of mesenteries which reach the oesophagus.
Thus in Zealia crassicornis, according to the Hertwigs (’79), all
the mesenteries, of which there are over 100, reach the cesopha-
gus, while in Lezotealia nymphaa, in which the mesenteries are
arranged in six cycles, only those of the first three cycles, 2.2.
twenty-four, are perfect, and in Bunodes teniatus we have seen
that twelve of the twenty-four perfect mesenteries were not
attached to the cesophagus throughout its whole length. Avz/ac-
tinta may be regarded as the one extreme in the number of
perfect mesenteries, and Zealia crassicornis as the other.

The verrucal nature of the ectodermal elevations may per-
haps be of considerable importance from a systematic point of
view, but this point has been already alluded to.

Sub-tribe DENDROMELIN.

Hexactiniz with the tentacles simple and arranged in cycles
on the margin. The upper part of the column immediately
below the margin provided with dendritic processes (pseudo-
tentacles). Base adherent.

This sub-tribe is established for the reception of two very
remarkable genera, Ledrunea, occurring in the West Indies in
shallow water, and Ophiodiscus, obtained by the “ Challenger”
in deep water (2160 and 1375 fathoms) in the Southern Pacific.
The specimens of the latter genus were unfortunately in a very
imperfect condition when examined by R. Hertwig, who de-
scribed them (’82), and the only evidence of the existence of
the peculiar processes which form the characteristic feature
of the group was a single, delicate, short-stemmed, much-
branched structure, enclosed in the same piece of cloth as the
four specimens of the genus that were obtained. It was found
quite unattached to any of the specimens, and presumably had
been torn away by the rough treatment the specimens appeared
to have suffered, no doubt from the dredge. The coelenterate
nature of this structure is almost certain, and that it belonged
to the specimens with which it was enclosed seems equally so,
and, though absolute certainty is wanting, yet it seems proper
to associate the Ophiodisci with Lebrunea. The peculiar form

32 McMURRICH. (Vou. III.

Eumenides ophiseocoma described by Lesson (28) for New
Guinea may, perhaps, be distantly related to the forms referred
to this sub-tribe, but differs in so many points that it cannot be
included with them.

Hertwig associated Ophzodiscus with the Paractinidz, which
belong to the sub-tribe Actininz as defined in this memoir, on
account of the circular muscle being imbedded in the mesogleea,
at the same time holding open the question as to the propriety
of erecting the genus into a special family. Since the various
sub-tribes are characterized by the nature of the tentacles, and
since the possession of the peculiar pseudo-tentacles, to employ
the name Hertwig has applied to them, is so characteristic, I
have thought it well to establish for the two genera, not merely
a new family, but a new sub-tribe, making the division which
they constitute of equal importance to the Stichodactyline or
Thalassianthine, This sub-tribe is probably more nearly allied
to the Actininz than to the other sub-tribes of the Hexactinia,
since the tentacles are arranged in cycles and not radially, and
are simple and conical. Their situation on the margin is an
important point, however, which in addition to the possession
of pseudo-tentacles distinguishes the sub-tribe from that of the
Actininz, and associates it, to a certain extent, with the Sticho-
dactylinz, in many of which the simple tentacles are marginal
in position. Duchassaing and Michelotti considered the genus
Lebrunea to be close to Phyllactis, but such an alliance is
unquestionably erroneous. The pseudo-tentacles have no rela-
tionship either in position or structure to the fronds of the
Phyllactidz.

The separation of the two genera, Lebrunea and Ophiodiscus,
in distinct families will probably be found necessary eventually,
inasmuch as the differences between them, such as the presence
in one and the absence in the other of a circular muscle, and
the specialization of the mesenteries into muscular and gono-
phoric cycles in Ophzodiscus, are probably of more than generic
importance. But until a greater number of forms belonging
to the group have been discovered, and their structure thor-
oughly studied, the establishment of separate families seems
unnecessary.

INOw 1.3] ACTINIARIA OF THE BAHAMAS. 33

Genus LEBRUNEA, Duch. and Mich.
Synon. — Lebrunea — Duchassaing and Michelotti, 1860.

Base firmly adhering to foreign bodies; tentacles in several
cycles ; pseudo-tentacles, six in number, dichotomously branch-
ing; no sphincter muscle, and no specialization of muscular and
gonophoric mesenteries.

6. Lebrunea neglecta, Duch. and Mich. (PI. 1., Fig. 7; Pl. IIL,
Figs. 11-14.)

Synon. — Lebrunea neglecta— Duchassaing and Michelotti, 1860.

Two specimens of this species were obtained at the Bahamas,
both of which were discovered by members of the Laboratory,
who were engaged in making collections for the University of
Pennsylvania. Dr. Charles Dolley, who was in charge of the
collections, kindly allowed me to make a drawing of one of the
specimens, and on my return generously placed it at my disposal
for detailed examination. The opportunity thus presented of
examining such an interesting form, I eagerly accepted, and I
desire here to offer to Dr. Dolley and his assistant, Mr. M.
Greenman, my sincere thanks for their courtesy. The other
specimen obtained is in the Museum of the University of
Pennsylvania.

Like those obtained by Duchassaing and Michelotti at St.
Thomas, the Bahama specimens were found attached to the
banks of coral rock near the shore. In color our specimens
differed somewhat from those obtained by the authors just
mentioned, whose description I here quote: “Corps cylindrique,
plissé transversalement, 4 couleur bleudtre avec des taches
blanches, de 1-2 pouces de hauteur. Disque large de 6-7
lignes; bouche grande et blanchatre; tentacules subégaux et
a peu pres de méme longueur que le diamétre, colorés en rouge-
atre dans leur moitié inférieure, et blanc dans la reste de leur
étendue. La couleur bleudtre des appendices change et devient
jaunatre aux derniéres ramifications.” The specimen I exam-
ined was colored as follows (Pl. I., Fig. 7): Column purplish
brown ; pseudo-tentacles seal-brown, the ultimate ramifications
being white. Disc and tentacles paler brown, the latter being
whitish at the tips. The disc was transparent, allowing the

34 McMURRICH. [Vot. III.

yellowish mesenterial filaments to show through, and was
marked with six paler lines radiating from the mouth towards
the bases of the tentacles of the first cycle. Peristome white,
with the gonidia a more opaque white.

The base is firmly adherent, apparently slightly larger in
diameter than the column, measuring 2.5 cm., at least so it is
in the preserved specimen, it being impossible to see either it
or the column in the fresh specimens owing to the position of
the tentacles. The column in these latter measured about
2.9 cm. in height; in the preserved specimens the height was
2 cm., and the diameter about the same. The surface of the
column is thrown into transverse folds, and a close examination
shows numerous minute tubercular elevations, produced, as
sections show, by slender filiform processes of the mesoglcea.
No special sphincter muscle is present, a circumstance which
distinguishes the genus from Ophiodiscus, as already noted, but
the general circular musculature of the column wall is fairly well
developed, the mesogloea being raised into short unbranched
processes which support it. The ectoderm consists principally
of glandular cells, and measures about 0.817 mm. in thickness ;
the mesogloea is thin, averaging only 0.04 mm. in thickness,
though it varies somewhat; while the endoderm, containing
numerous “ yellow cells,” is about 0.065 mm. in thickness.

The disc is flat, and transverse sections show a fairly well-
developed muscular layer, entirely ectodermal, however ; that is
to say, it is arranged on elevations of the external surface of
the mesogloea, and is not at all imbedded within its substance
as in Ophiodiscus. The gonidial angles of the mouth are very
distinct. The tentacles are marginal, simple, and cylindrical,
hanging down over the column as in Ophiodiscus. They are
long, measuring about 3 cm. in length, and are arranged in
several cycles, their formula being apparently 6, 6, 12, 24, 48,
96 (?). In structure they resemble closely the disc, there being
a well-defined nerve layer (Pl. III, Fig. 13). The difference
in the structure of the inner and outer surfaces of the basal
portion of the tentacles which Hertwig describes in Ophzodiscus
does not obtain here, although their marginal situation does
entail some peculiarities. Thus, immediately at the base in
some of the tentacles an endodermal musculature can be per-
ceived as well as an ectodermal, which latter again is frequently

No:-t] ACTINIARIA OF THE BAHAMAS. 35

absent on one surface. The endodermal musculature is evidently
a continuation upwards of that of the column wall, but it soon
disappears, and a very short distance above the base the tenta-
cles throughout their whole circumference resemble the disc.

The pseudo-tentacles are six in number, and not five, as Du-
chassaing and Michelotti (60) describe, one having evidently
been overlooked by them, or else they chanced upon an abnor-
mal specimen. In both of the specimens obtained at New Provi-
dence six were present, and there can be no doubt but that this
is the normal number. They alternate with the six primary
tentacles. Each has a somewhat elongated stout basal portion,
which measures 3.8 cm. in length by 0.8 cm. in diameter. This
divides into two equal stems (Pl. III., Fig. 11), which again
dichotomize many times until a dendritic structure is produced,
which projects some distance beyond the decurved tentacles.
In structure the pseudo-tentacles are somewhat peculiar. Trans-
verse sections through the basal portion (Pl. III., Fig. 12) show
the ectoderm to be identical in composition with that of the
column, and the ectodermal surface of the mesogloea is raised
into fine processes as in the column-wall. The musculature of
the endoderm is, however, very characteristic, bands of muscle
cells (wz) being arranged at intervals around the circumference,
the surface in the portions intervening between the bands being
destitute of muscle cells. A nervous layer can be traced all
the way round, but is only well developed over the bands, being
in the intervals exceedingly delicate and sometimes scarcely
discernible. In the finer branches this arrangement of the
endodermal muscles becomes much less distinct, and finally dis-
appears altogether. In the terminal branches the ectoderm is
markedly changed in structure, becoming densely loaded with
nematocysts, while elsewhere, as in the column, these are absent.
It may be remarked here that this is the only anemone of all
those I examined and handled which stung at all severely, though
this may in part be due to the pseudo-tentacles having come in
contact with the more delicate skin between the fingers. Prob-
ably in the same circumstances the stinging powers of Dzsco-
soma would have been quite as marked.

I was unable to ascertain the number of the mesenteries, but
they are quite numerous, a pair probably corresponding to each
tentacle. Half of the pairs are decidedly larger than the others,

36 McMURRICH. [Vou. III.

the long and the short pairs alternating, the former only being
perfect. The mesogloea is exceedingly delicate. Longitudinal
muscles, moderately strong (PI. III., Fig. 14), are developed on
all the mesenteries, as well as a very weak parieto-basilar. All
(including the directives?) are gonophoric. The specimen ex-
amined was a female, and the number of ova present seemed
very great. From this description it will be seen that the
arrangement of the mesenteries is very different from what
occurs in Offhiodiscus, in which the first three cycles, two of
which are perfect, alone possess longitudinal muscles and are not
gonophoric, the reproductive organs being limited to the non-
muscular mesenteries of the fourth cycle. These differences,
taken with others which have already been pointed out, seem to
justify a separation of the two genera into distinct families ;
but, as already remarked, such a separation is as yet hardly
necessary.

Sub-tribe STICHODACTYLINE
= Family Stichodactyline, Andres, 1883.

Hexactiniz, in which some of the interseptal spaces com-
municate with more than one tentacle, the latter being thus
arranged in radial series encroaching upon the central portion
of the disc. The tentacles are in some cases all of one form,
z.e. tentacular, and in other cases are of two forms, some being
tentacular and some frondose or of varying form. Base ad-
herent.

Family Discosomide.

Synon. — Discostominz — Verrill, 1868.
Discosomide (pars) — Klunzinger, 1877.
Discosomidz — Andres, 1883.

Stichodactylinze, with tentacles of only one form, short and
tentacular, and covering the greater portion of the surface of
the disc. Sphincter muscle strong and circumscribed.

This family as here limited agrees with Andres’ sub-family of
the same title. The term employed by Verrill owes its origin
to the proposed change of the name of the principal genus
Discosoma.

No. 1.] ACTINIARIA OF THE BAHAMAS. 37

Genus Discosoma, Leuck.

Synon.— Priapus (pars) — Forskal, 1775.
Actinia (pars) — Ellis, 1767.
Hydra (pars) — Gmelin, 1788.
Discosoma — Leuckart, 1828.
Actinodiscus — Blainville, 1830.
Discostoma — Ehrenberg, 1834.

Discosomidz, with the column either smooth or furnished
with verrucz towards its upper portion. Tentacles rather small
and finger-shaped, covering the greater portion of the disc.
Sphincter muscle strong, and of the circumscribed variety.

The earlier names under which the members of this genus
were included do not call for comment. Ehrenberg (’34) altered
the term bestowed by Leuckart, considering it inappropriate ;
and Verrill adopted this altered name (’68) on the ground that
the term Discosoma had been applied to an Arachnid and Dis-
cosomus to a reptile by Oken. In retaining Leuckart’s original
name I have followed Andres, since, as he points out, its appli-
cation to the Actinian has the priority, the Arachnid not having
been named till 1830.

7. Discosoma anemone (Ellis), Duch. (Pl. I., Fig. 8; Pl. IIL.,
Pigs. 15-16; Pl. IV., Fig. 1:)

Synon.— Actinia anemone, n. sp. — Ellis, 1767.
Hydra anemone — Gmelin, 1788.
Discosoma anemone — Duchassaing, 1850.
Actinia helianthus, n. sp. — Ellis, 1767.
Hydra helianthus — Gmelin, 1788.
Discosoma helianthus — Milne-Edwards, 1857.

I have included under the name Dzscosoma anemone both
forms described by Ellis, believing that the differences between
the two forms indicated by that author were simply due to dif-
ferent degrees of contraction or to age.

This species is very common in the neighborhood of New Prov-
idence, especially near the quarantine station on Athol Island,
and also occurs at Abaco Island of the Little Bahama reef.
It is found along the sandy shores lying buried in the sand, with
the tentacle-covered disc exposed, sometimes attached below to
loose stones or buried sticks, but more frequently is unattached.

38 MCMURRICH. [VoL. III.

Duchassaing and Michelotti have described it (60-66) from
Guadeloupe and St. Thomas. ,

In color (Pl. I., Fig. 8) the column is cream-white shading off
above into a brown, occasionally dark seal-brown. The disc is
brown, with opaque white patches. The tentacles are greenish
brown or white, those of each color being arranged in groups,
so that the surface of the animal has a variegated appearance.
According to Duchassaing and Michelotti (60) the color of the
tentacles changes so that in the space of some hours they can
pass from one color to the other, but I did not observe this
peculiarity. The gonidia are well marked, being of a canary-
yellow color, while the stomodzeum is white.

The base is usually somewhat smaller than the column, and is
frequently very irregular in shape. It is capable of adhering
firmly to various objects, but not infrequently I gathered speci-
mens which did not seem to be attached to any solid body, but
simply imbedded in the sand. The column is capable of con-
siderable extension, but in their normal condition most speci-
mens are more or less contracted, measuring about 1.5-2, occa-
sionally 5 cm. in height. In an aquarium, however, where there
was no sand in which the animals might imbed themselves they
extended much more, one form measuring in such conditions
13.5 cm.in height. The upper portion of the column is provided
with verrucz arranged in vertical series, which are, however, in
many cases very indistinct, being of the same color as the col-
umn. In some specimens, on the other hand, they stand out
very prominently, being of a brownish or greenish brown color.
In structure these verrucz resemble closely those of Az/actinza,
being characterized by the absence of the large club-shaped
glandular cells which are elsewhere present in the ectoderm of
the column. The layer of small pyriform cells, so evident in
Phymanthus (q. v.), was not clearly distinguishable in sections,
though there were apparently numerous peculiar cell elements
in that region of the verrucal epithelium in which the pyriform
cells occur in Phymanthus.

An exceedingly well-developed circumscribed endodermal
sphincter muscle (Pl. III., Fig. 15) is present, notwithstanding
that the animals do not seem to be able to retract the tentacles ;
in Polysiphonia tuberosa, in which there is a mesoglceal sphinc-
ter muscle, R. Hertwig (’82) observed the same absence of a

No. 1.] ACTINIARIA OF THE BAHAMAS. 39

retraction of the tentacles by the folding in of the upper part
of the column over them. In transverse sections the sphincter
muscle of Dzscosoma is oval and attached to the column wall by
a distinct pedicle, the mesogloea of which breaks up quickly
into a number of processes, although towards the inner side a
prolongation of it, much reduced in size, is continued on towards
the extremity of the swelling, processes arising from it in a
somewhat pinnate manner. A little below the point of attach-
ment of the pedicle to the column wall are a series of well-
marked muscle processes, succeeding which comes a short in-
terval in which all such processes are wanting ; below this they
again make their appearance, being now relatively small, how-
ever, and extend the rest of the way down the column.

The ectoderm of the column is raised into slight elevations
(Pl. III., Fig. 16), not sufficiently large, however, to be plainly
noticeable to the naked eye, or to give a tuberculate appearance
to the column. They are produced by solid conical elevations
of the mesogloea, and are very numerous and closely packed,
the ectoderm covering them being quite undifferentiated and
resembling in structure that which covers the walls in the
intervals between them. The endoderm cells throughout con-
tain numerous “ yellow cells.”

The tentacles are short finger-like processes, and are very
numerous in the larger specimens, their number approaching in
some cases 600. All the tentacles of each radial series commu-
nicate with the same intraseptal space, but the number in each
series is subject to considerable variation, and I was not able to
discover any law regulating this number. Some of the series
were very evidently longer than the others, extending nearly to
the mouth, but the length of these rows varied, as also did the
number of shorter rows between successive longer ones, there
being in some cases only two or three, in other cases five or six.
I endeavored by carefully dissecting away in succession the
mesenterial pairs, and the tentacles communicating with their
intra-mesenterial spaces, to determine the relation between the
number of tentacles, and the grade of the septum ; but the process
was one of considerable difficulty, and, so far as I carried it,
yielded no definite results. In structure the tentacles resemble
closely those found in members of the sub-tribe Actinine. The
ectoderm was exceedingly richly supplied with nematocysts,

40 McMURRICH. [Vou. II.

which perhaps give rise to the peculiar clinging power possessed
by the tentacles in fresh specimens. They adhere to the fingers
quite firmly when handled, and a quite decided effort is required
to detach them. I believe this to be due to the numerous
nematocysts, as I discovered no glandular or suctorial structures
in the tentacles. No sensation of stinging was observed, how-
ever, but this does not necessarily follow the penetration of the
hard skin of the hands by the threads of the nematocysts. In
the lower layer of the ectoderm is a delicate nervous layer.
The ectodermal musculature is longitudinal, and is by no means
strong, the mesogloeal processes being quite low. On the endo-
dermal side of the mesogloea are circular muscles, and the endo-
derm cells contain numerous “yellow cells.” In longitudinal
sections a fibrillar layer containing some nuclei could be ob-
served, separated from the mesogloea by the muscle cells; it is
evidently the endodermal nerve-layer, similar to that which the
Hertwigs have described (’79) in Zealia crassicornis. It is most
clearly seen just where the tentacles join the disc, becoming
rapidly indistinct towards the apex of the tentacles, so that in
that region it is impossible from my preparations to assert its
presence.

The small portion of the disc left uncovered by the tentacles
is smooth, and structurally presents no peculiar characters, the
musculature, like that of the tentacles, being weak. The mouth
is large, with well-marked gonidial folds.

The mesenteries are very numerous, varying, according to
the size of the individual, from 100 to 200 pairs, which are
alternately perfect and imperfect. The longitudinal and parieto-
basilar muscles are not particularly strong, the former being
limited to the outer portion and having the processes arranged
in a characteristic manner. A series of elevations of the meso-
gloea give rise to a number of radiating processes, which branch
to a slight extent, there being a few short and stout processes
in the intervals (Pl. IV., Fig. 1). The nearest approach to such
an arrangement that I am aware of has been described by
R. Hertwig in Polystomidium patens. The inner mesenterial
stomata are present, and are comparatively large; there is no
trace of the external stomata. The specimens examined were
females, and the reproductive organs were present on all the
mesenteries, with the exception probably of the directives. My

No. 1I.] ACTINIARIA OF THE BAHAMAS. 4!

preparations were not, however, quite satisfactory for the deter-
mination of the relation of the gonophoric and sterile mesen-
teries. A filamental apparatus is present.

Several specimens were obtained in various stages of division,
and there can be no doubt but that this species must be added
to the list of those which are known to reproduce non-sexually
in this manner.

The form described by Ehrenberg (34), Klunzinger (’77), and
others, from the Red Sea, occurring also at Mozambique, and
known as Discosoma giganteuwm (Forsk.), is very close to the one
here described, if one can judge by the descriptions which have
been given of it; but differs somewhat in size, measuring IO cm.
in height. It must, however, be considered a distinct species
until a further study of it has been made. It is worthy of
note that Forskal mentions the adhesiveness of the tentacles
of D. giganteum, which, as above stated, is very noticeable in
D. anemone.

Mosely, who first described the deep-sea forms Corallimorphus,
considered them most closely allied to Dzscosoma. R. Hertwig
(82), however, established a separate family for the genus while
recognizing the probability of a close similarity in structure to
Discosoma, but placing importance upon the nature of the ten-
tacles, which are of the knobbed variety and arranged in an
inner and an outer cycle, a tentacle of the former occurring on
the same intraseptal space with one of the latter cycle. He
also suggested a similarity to the Corynactida, which likewise
possess knobbed tentacles. It is evident, from the description
given above of Dzscosoma, that Corallimorphus cannot be placed
in the same family with it. The presence of the strong circum-
scribed muscle in the former genus at once distinguishes it,
there being no special circular muscle at all in the latter. A
study of Corynactzs is required to ascertain its nature in this
respect.

Family Ruopactip#&, Andres.

Synon. — Phyllactinine (pars) — Klunzinger, 1877.
Rhodactide = Andres, 1883.

Stichodactylinz with tentacles of two kinds. The margin is
furnished with tentacles of the ordinary kind arranged appar-

42 McMURRICH. [Vou. III.

ently in a simple cycle, while upon the surface of the disc, and
separated from the marginal tentacles by a naked space, are
numerous tuberculiform or lobed tentacles, arranged more or
less radially. No sphincter muscle, the musculature through-
out being very weak.

I have thought it proper to extend this family somewhat, so
as to include it in a genus referred by Andres to the family
Crambactide. My reasons for so doing will be given when
discussing the genus.

Genus RuopactTis, Milne-Edwards.

Synon. -— Metridium (pars) — Ehrenberg, 1834.
Actineria (pars) — Deshayes, 1837.
Rhodactis — Milne-Edwards, 1857.

Rhodactidz with smooth column. Marginal tentacles very
short and conical ; disc tentacles more or less lobed, arranged in
two groups, one, consisting of the greater number of tentacles,
towards the periphery of the disc, and the other separated from
the peripheral group by a naked space, and consisting of a few
tentacles only, situated around the mouth, and therefore labial.

8. Rhodactis Sancti Thome (Duch. and Mich.). (PI. I., Fig. 9;
Pl LV.) Pigs..2, 3.)

Synon. — Actinotryx Sancti-Thome — Duchassaing and Michelotti, 1860.
Actinothrix Sancti-Thome— Andres, 1883.

This form, first described by Duchassaing and Michelotti (60),
is made by them the type of a new genus. They, however, rec-
ognized its similarity to Rhodactzs, the distinction being that
“les appendices, qui avoisinent la bouche, sont simples et bilobés,
tandis que la disposition des tentacules placés entre les cou-
ronnes interne et externe est aussi différents.”” Andres, however,
considers this statement “quasi inintelligibile,” and believes that
the species has nothing to do with Rhodactzs, and places it, along
with the genus Cvambactis, in another family. After having
studied this so-called Actinothrix, I have come to the conclusion
that it zs a Rhodactis, the difference between it and Rhodactzs
rhodostoma being of specific and not of generic importance.

Rhodactis Sancti Thome@ is not uncommon at New Providence,
occurring firmly attached to the coral rock in shallow water. It

No. 1.] ACTINIARIA OF THE BAHAMAS. 43

is exceedingly difficult to detach it without injury, and when
irritated secretes an enormous amount of mucus, its separation
from the rock being thereby rendered more difficult. In color
(Pl. I., Fig. 9) the column is of a brownish purple, frequently
with a more or less greenish tinge; the disc is similar in color,
with green bands radiating from the raised peristome towards
the margin; the peripheral tentacles are pale bluish green, with
brown tips, the disc tentacles being seal-brown or a somewhat
lighter shade of the same color; the mouth and cesophagus are
white.

This form is known from St. Thomas, where it was originally
discovered. Some of the specimens obtained at New Provi-
dence are sufficiently light colored as to agree fairly well with
the description given by Duchassaing and Michelotti of the
St. Thomas examples.

The column measures about 1.6 cm. in height, and is smooth.
It expands considerably above, the margin being frequently, in
full expansion, folded back so as to conceal the column. No
special sphincter muscle is present, and in fact the circular mus-
cles of the column are throughout exceeding feebly developed,
a fact which agrees with the small power of infolding the disc
which these forms possess ; in a single instance only did I meet
with an individual which had this power. The ectoderm of the
column is thrown into longitudinal series of minute elevations,
each series corresponding with an interval between two mesen-
teries, and the elevations being formed by delicate processes of
the rather thin mesogloea (0.85 uw). So far as could be ascer-
tained there is a complete absence of cnidoblasts in the ecto-
derm, the only cells present being apparently glandular, the
contents of which do not stain, sections through the column
wall having thus a very characteristic appearance. The endo-
derm also contains gland cells, and is richly packed with “ yellow
cells:”

The margin is occupied by the single row of peripheral ten-
tacles, which are short, cylindrical, and abruptly acuminate.
They vary somewhat in size, a small one usually alternating
with a larger one, though frequently two or three small ones
will intervene between two succeeding large ones. The num-
ber of these tentacles varies; in larger specimens they are
somewhere in the neighborhood of 150.

44 - McCMURRICH. [Vot. III.

The disc is covered for the most part with short, stout tenta-
cles, whose surface is elevated into a varying number of tuber-
culiform or short, finger-like processes. They are arranged
somewhat irregularly, and are situated principally midway be-
tween the margin and the mouth, a circle of them, however,
surrounding the mouth, being separated by a considerable naked
space from the rest. The portion of the disc adjacent to the
margin is also naked. There is no trace at the bases of the
tentacles of any such depressions with elevated margins as occur
in Rk. rhodostoma, but this must be regarded as a specific dis-
tinction only, and not generic. The histological structure of the
disc, marginal tentacles, and disc tentacles are similar through-
out. The ectoderm (Pl. IV., Fig. 2, ec’) is thin, measuring in a
disc tentacle, somewhat contracted, 34, on the disc near the
margin when expanded, 27.2 u. A peculiar feature of the ecto-
derm throughout is the entire absence of nematocysts, there
being on the other hand numerous gland cells. The muscular
layer is exceedingly delicate, a single row of muscle cells lining
the smooth external surface of the mesogloea. The mesogleea,
like the ectoderm, is very thin, measuring, in the disc tentacles,
10.2 to 13.6 w, and in the disc, 3.4. The endoderm, however,
presents a most remarkable appearance, differing from that of
any Actinian I have yet studied. Its general characters are
well shown in Pl. IV., Fig. 2, ez’. It consists of high glandular
cells, measuring from 0.136 to 0.17 mm., and filled with a clear
substance which does not stain, the cell walls and much com-
pressed nuclei standing out very clearly. The cavity of the
tentacles is filled with the secretion of these cells, which is
apparently a perfectly homogeneous coagulable fluid. Numer-
ous “yellow cells” are imbedded in the contents of the cells,
especially towards their proximal ends.

The mouth is large and almost circular, and is elevated con-
siderably above the surface of the disc. The stomodzum is
raised into strong folds,as may be seen from PI. IV., Fig. 3.
The gonidia are not at all well marked ; in fact, it is not possible
to distinguish them.

The mesenteries, like the other regions of the body, have
the muscular layers very weakly developed, the longitudinal
foldings of the mesogloea, so characteristic in other species,
being almost undeveloped and represented only by very slight

No. 1.] ACTINIARIA OF THE BAHAMAS. 45

rounded elevations. The arrangement of the mesenteries I
was not able to make out satisfactorily. The majority of them
are perfect, the imperfect ones being usually quite small and
appearing to have no regular arrangement. Thus there would
be several perfect pairs in succession, followed by one or two
imperfect pairs, alternating with perfect ones, and then several
more perfect pairs, and so on. It would seem that normally all
the mesenteries are perfect, but that a few, for some cause or
other, remain undeveloped. All the mesenteries are situated at
equal distances, so that the intra- and inter-mesenterial spaces
are about equal in width. It is difficult, owing to this and to
the very slight development of the longitudinal muscles, to orient
the pairs properly, but there are probably two pairs of directives,
as in other forms, although I was able to make out with cer-
tainty only one of them. R. Hertwig (82) has described a
species in which this is the normal relation, and has founded
upon it the tribe Monauleze. In its general character, however,
Rhodactis differs greatly from Scytophorus, the only genus at
present known to belong to the tribe, and on the other hand
resembles forms which possess the two pairs of directives, so
that I believe that it possesses the second pair, and that its
apparent absence in the specimens examined was due to the
unsatisfactory nature of the preparations which I studied. The
number of the mesenteries is comparatively large ; in a small
specimen I counted 48 pairs, and in another 52; but in a larger
one, judging from the number of the series of ectodermal ele-
vations, there must be in the neighborhood of 150.

The endoderm of the mesenteries is of the same nature as
that of the disc, and requires no further description. Imbedded
in it were found in the specimens examined numerous cysts,
measuring about 68 w in length by 27 w in breadth, which looked
almost like encysted nematode parasites, the comparative rarity
of their occurrence lending somewhat to the illusion. Careful
study, with high magnification, showed them to be large nema-
tocysts. The thread contained in the interior is not very long,
and is finely and obliquely striated. Occasionally considerable
numbers of these bodies occur together, apparently more espe-
cially in the mesenterial filaments, but their number taken alto-
gether is comparatively small. They were present in the endo-
derm of the disc (Pl. IV., Fig. 2, ze) as well as in that of the

46 McMURRICH. [Vou ii;

mesenteries, and were, so far as I could discover, the only nem-
atocysts present.

None of the specimens examined showed any traces of repro-
ductive organs. The spawning season was probably just over,
as I obtained a few free-swimming larvz from a vessel in which
a couple of this species were kept over night.

Genus HETERANTHUS, Klunz.

Synon. — Ricordea — Duchassaing and Michelotti, 1860.
Heteranthus — Klunzinger, 1877.
Actinothrix — Andres, 1883.

Rhodactidz, with short marginal tentacles, forming a single
row, and with the disc covered with tuberculiform tentacles
arranged radially.

The type species of this genus is Heteranthus verruculatus of
Klunzinger (77), which has the characters given above. Cer-
tain features presented by it are not, however, met with in the
Bahaman species ; for instance, the verrucze of the column are
absent in the latter form, as are also the bunches of tubercles
on the margin. These may be looked upon, however, as specific
differences, and Klunzinger’s definition has consequently been
altered. Andres (83) associated A. verruculatus with the Ac-
tinotryx Sanctt Thome of Duchassaing and Michelotti, retaining
that generic title inasmuch as it was the older. I have stated
my belief that Actznotryx is really a Rhodactis, and consequently
that term should be disregarded, and the one employed by Klun-
zinger retained.

I have also departed from Andres’ arrangement in placing
Heteranthus in the family Rhodactidz. That author associates
it with Crambactis in the family Crambactidz. The tubercular
disc tentacles in Heteranthus, however, are much more similar
to the lobed ones of R/odactis than to the foliose ones of Cram-
bactis, and furthermore, the marginal tentacles of Heteranthus
and Rhodacizs are in a single row, while those of Crambactzs are
arranged in several cycles. Consequently I associate the two
former genera together in one family, leaving Crambactis as the
sole genus of another.

The term Rzcordea, proposed by Duchassaing and Michelotti
(60) as a new genus for the reception of the species to be de-

No: te] ACTINIARIA OF THE BAHAMAS. 47

scribed below, has the priority over Klunzinger’s term; but,
since the characters which were assigned to it by its authors
are, if anything, specific and not generic, I have ventured to
disregard its priority. The justice of this is no doubt open to
question, but in this case I think that such a substitution has
much in its favor. Not only does Klunzinger’s definition char-
acterize the genus, which cannot be said of Duchassaing and
Michelotti’s, but the term Heteranthus itself is preferable as in-
dicating a character of the forms to which it is applied, and is
much more in harmony with Actinian nomenclature. The char-
acters assigned to Rzcordea will be discussed below in connec-
tion with the description of the species.

9. Heteranthus floridus (Duch. and Mich.). (Pl. L, Fig. 10;
Pl. IV., Figs. 4-5.)

Synon. — Ricordea florida — Duchassaing and Michelotti, 1860.

This form occurs not unfrequently adhering to stones in shal-
low water, and was usually found in association with RA. Sancti
Thome. Like that species it adheres very firmly to the surface
of the rocks, so that it is exceedingly difficult to detach it with-
out injury, especially since when touched it throws off large
quantities of mucus.

In color (PI. I., Fig. 10) it is pale flesh color below, shading off
above into a purplish brown. The disc and peristome are also
of a purplish brown, with a very decided green tinge. The
outer tentacles are green, and the disc tentacles of the same
color as the disc. The mouth and stomodzum are white.

The base, on account of its firm adhesion to the rock and its
accommodating itself to the uneven surface of attachment, is
usually very irregular and folded so as to project into the cavity
of the body, and it retains these foldings to a greater or less
extent when removed from the rock. This circumstance, to-
gether with the small height of the specimens, rendered it very
difficult to obtain preparations from which the arrangement of
the mesenteries, etc., could be accurately determined.

The column is low, measuring in height 0.45 cm., and in
diameter about 1.2 cm. Its outer surface is raised into minute
tubercles hardly visible to the naked eye, and supported by
exceedingly delicate, frequently somewhat branched, processes

48 McMURRICH. (VoL. III.

of the thin mesogloea (PI. IV., Fig. 4). I never observed these
tubercles to be capable of causing the adhesion of particles of
sand, etc., although the ectodermal cells covering them seem
to be somewhat different from those in the intervals, being
more delicate, resembling somewhat those characteristic of
verruce. The surface of the elevation is not depressed as in
verruce, and they differ in this respect from these of H. ver-
ruculatus, which Klunzinger describes as being provided with
verrucze situated especially towards the upper part, but often
extending almost to the base. The ectodermal cells are deli-
cate, but present no remarkable characteristics. The endoderm
contains numerous gland cells, and is richly provided with “ yel-
low cells.” The muscular layer throughout is very weak, and
there is no trace of a sphincter muscle, unless two or three pro-
cesses of the mesogloea, widely separated, and similar to those
which support the ectodermal tubercles, may be considered as
representing it.

The margin bears a number of short conical tentacles similar
to those of Rhodactis. No bunches of tubercles are to be
observed similar to those of H. verruculatus. The disc, which
measures I.3 cm. in diameter, is covered towards the periphery
with rows of short tuberculiform tentacles arranged radially.
There is considerable irregularity in the length of the various
rows ; their number is about 36, though it is difficult from my
specimens to give an exact number. In structure these tenta-
cles are characterized by the small development of the muscular
layer, by the total absence of nematocysts as in Rhodactis, and
especially by the nature of the ectoderm cells of the apex (PI.
IV., Fig. 5). Over the general surface they present no pecu-
liarities, but just at the apex, where in preserved specimens
there is a translucent circular spot, the cells become exceedingly
delicate and closely packed together, so as to resemble very
closely in general appearance what has been previously described
for the verruce of Az/actinia. The mesogloea of the tentacles
and disc, like that elsewhere in the body, is very thin. The
central portion of the disc is bare, and from it the peristome
rises up somewhat abruptly, so that the mouth is some distance
above the surface of the disc. The mouth is almost circular,
and the gonidial angles cannot be distinguished. The walls of
the stomodzeum are raised into folds as in Rhodactts.

No. i] ACTINIARIA OF THE BAHAMAS. 49

I was not able to make out in this form the arrangement of
the mesenteries. The longitudinal and parieto-basilar muscles
are as slightly developed as in Rhodactis, and, as in that form,
the inter- and intra-mesenterial spaces are about equal in width,
I counted about 28 pairs of mesenteries in a fair-sized speci-
men; of these 12 were perfect and the rest imperfect, the
latter usually but not always alternating with the perfect ones.
I could not distinguish with certainty the directives. None of
the specimens examined possessed reproductive organs. The
endoderm cells of the mesenteries, though mostly glandular,
were by no means so markedly so as in Rhodactis, nor did I
observe any of the large nematocysts characteristic of that
form.

This species I observed in the process of fission. In one
specimen the process was nearly completed, the two individuals
being quite distinguishable, and united to each other throughout
an extent equal to about half the diameter. In another case,
however, the process had not extended nearly so far, the only
evidence of the fission being the presence of two distinct
peristomal elevations, each with a mouth, upon the disc, and
a crowding of the rows of disc tentacles on the portion of the
disc common to the two mouths.

Duchassaing and Michelotti (60) describe this form under
the name of Azcordea florida. The genus is defined as consisting
of forms which, though simple when young, become composite
when their development is complete; z.¢.,at this stage the animals
have five mouths situated at the centre of the disc, which is
elsewhere covered with short obtuse tentacles, not completely
retractile. In their second paper (’66) they state their belief
that the genus presents relations to Dzscosoma on account of the
tentacles being non-retractile, and the disc not being able to
close completely. The single species, which they describe as
being common at St. Thomas, is of a dark green or blue, pre-
senting a variety with reddish tentacles. The figure of it which
they give shows that it is identical with that just described, not-
withstanding that no notice is taken of the marginal tentacles.
The occurrence of several mouths on the disc is certainly a
peculiar feature, and one that would, if no other forms having
the same arrangement of the tentacles were known, lead one to
make it a generic distinction. There can be no doubt, however,

50 MCMURRICH. [Vot. III:

that it is not of such importance. It is produced by the non-
completion of the process of division, and the forms might be
compared to such corals as Fungia or Mantcina, which, though
individual polyps, still possess several mouths. The remarkable
thing about it is its general occurrence, since Duchassaing and
Michelotti seemed to have found it almost universal, while it
was present in several of my specimens.

Although the facts made out concerning the histology of R/o-
dactis and Heteranthus are so meagre, yet sufficient has been
ascertained to confirm the conclusion as to the similarity of these
two forms, which was arrived at from the study of their external
characters. Thus they have in common the absence of a circular
muscle, the weak musculature of mesenteries, disc, and ten-
tacles, the elevation of the cesophagus wall into a number of
very pronounced folds, the excessive proportion of glandular
cells in the endoderm, and the very slight development of nema-
tocysts. Taking these points in conjunction with the similarity
in the form of the tentacles, the propriety of associating these
two genera in the same family is, I think, established.

Family Phymanthidz, Andres.

Synon. — Phyllactinize (pars) — Klunzinger, 1877.
Phymanthide — Andres, 1883.

Stichodactylinz provided with two kinds of tentacles, mar-
ginal ones large, tuberculiferous or pinnate, and discal ones small
and papilliform.

It seems a question whether this family should not be fused
with that of the Phyllactide. Tuberculiferous and foliose
tentacles are merely different degrees of the same kind of
specialization, and the papilliform discal tentacles are simply
very much shortened conical ones. It seems well, however, to
leave them separate just now.

Genus PHymMantTuus, M.-Edw.

Synon. — Actinia (pars) — Lesueur, 1817.
Actinodendron (pars) — Ehrenberg, 1834.
Phymanthus — Milne-Edwards, 1857.

Phymanthide with the column provided with longitudinal
rows of verrucz in its upper part. No sphincter muscle.

No: 1: ACTINIARIA OF THE BAHAMAS. 51

10. Phymanthus crucifer (Les.), Andres. (Pl. IL, Fig. 1;
Pl. IV., Figs. 6-11.)

Synon. — Actinia crucifera— Lesueur, 1817.
Cereus crucifer (Actinia) — Duchassaing and Michelotti, 1866.
Phymanthus cruciferus — Andres, 1883.

Several specimens of this form were obtained, usually fastened
to blocks of coral rock in shallow water.

The column (PI. II., Fig. 1) is of a cream-white ground color,
varying toward pinkish at the base, and extending up from the
base are irregular streaks of crimson. The verruce are of a
rich crimson and are very evident upon the whitish ground.
The tentacles are brown, marked with transverse bars of white
somewhat elevated above the general surface. The disc is
brown, in some specimens covered with irregular blotches of
white, and in all cases showed a very marked greenish iri-
descence when viewed with the light falling on it obliquely.

The base is firmly adherent, and only slightly larger than the
column. This varies considerably in length. When fully con-
tracted, the animal is only a couple of centimetres high and
conical in shape, the disc being widely expanded, while the col-
umn is much contracted towards the base. When expanded, it
measures 8.3 cm. in height and 4.75 cm. in diameter. The
verrucze are limited to the upper portion of the column, and are
arranged in vertical rows. A transverse section through one of
these structures and the adjacent column wall (Pl. IV., Fig. 6)
shows a marked difference in the histological structure of the
two parts. In the general ectoderm of the column (ec) are
many club-shaped glandular cells measuring 6.4 ~ in diameter,
whose contents are exceedingly granular, and also numerous
cnidoblasts containing smooth capsules measuring 16.8 in
length and 2.4m in diameter. The ectoderm of the veruccz
(mec), on the other hand, is composed of cells which took the
staining (Borax Carmine) much more deeply, and gave the
appearance of very fine fibrillation to the layer. Towards the
mesogloea, but separated from it by a short interval, are numer-
ous bodies of a somewhat oval shape (fy) which take the stain-
ing very deeply. Sections through the verrucae were macerated
for some time in 0.2 per cent acetic acid. The general ecto-
derm of the column separated very readily from the mesoglcea,

52 McMURRICH. [Vo. III.

but that of the verrucz remained firmly attached, and could only
be separated with difficulty, as in Awdactinia and Helactis.
When separated, the cells composing it were seen to be exceed-
ingly delicate and very uniform in thickness, being only slightly
dilated towards the outer extremity. There were none of the
glandular cells or cnidoblasts of the general ectoderm present.
The darkly stained bodies seen in the sections were found to be
small oval or pyriform structures, measuring 14.4 in their
longer diameter, and with a maximum thickness of about 4.8 wu.
It is possible that they may be glandular, but I was unable to
discover that they possessed any connection with the exterior,
though some of the more perfectly isolated ones seemed to be
broken off at one end, and there may possibly have been a very
fine process or duct extending to the surface. There appear to
be no nerve cells present in the verrucal epithelium, unless these
pyriform bodies be such, and no muscle cells.

Von Heider observed (’77) in his investigation of Hedlzactis
bellis (Sagartia troglodytes) that the ectoderm of the verrucze was
less readily separable from the mesogloea than that of the general
surface, and also perceived the difference in the shape of the cells
which he describes as follows: “Eine solche (Saugwartze) mit
Osmium oder Alkohol gehartet und untersucht (Fig. 38) erweist
sich als aus zahlreichen parallelen Stabchen zusammengesetzt,
die spindelformig und beiderseits ziemlich spitz endend, im
Innern fein gekérnt erscheinen und so dicht aneinander gedrangt
sind, dass die einzelnen Elemente nur am Rande des Schnittes,
wo sie sich isoliren, deutlich zu sehen sind.” According to my
observations, the spindle-shape was not so universal a character-
istic, though some cells presented it. Von Heider did not
observe any of the peculiar pyriform cells, and it is possible that
they may not be present in the verruce of Hedzactzs, though it
seems more probable that they were overlooked, as they might
very readily be, in Bunodes teniatus, for instance.

With regard to the mode of action of the verruce in pro-
ducing the adherence of foreign bodies, Gosse (’60) was of the
opinion that it was a process of suction, agreeing in this with
Hollard (51) and Haime (’§4). I do not think this is the case,
however. The absence of muscle cells in the verrucal epithe-
lium, and the abrupt discontinuity of the muscle processes at the
edge of the verruce as seen in sections of Awlactinza, are

Ne. 1. ] ACTINIARIA OF THE BAHAMAS. 53

against it. Von Heider’s idea, that it is due to a special secre-
tion produced by the ectodermal cells, seems much more in
accordance with the histological structure. I was inclined at
first to consider the pyriform cells the producers of the secre-
tion, but am now undecided as to whether they are not really
nerve ganglion cells. They occupy the position of the nerve
layer of other parts of the body, and their slight development
in some species seems to indicate that they are not directly con-
cerned in producing the adherence of foreign bodies. I regret
that I was unable to study maceration preparations of fresh
specimens, from which, no doubt, this point might be settled ;
and it would be exceedingly interesting, in connection with the
physiology of secretion, to make such observations, and deter-
mine the existence or non-existence of nerve cells in the
verruce.

The mesogloea of the column wall is rather thick (Pl. IV.,
Fig. 7), and is raised into numerous obtuse elevations. The
endoderm is as usual abundantly supplied with “yellow cells.”
There is no special sphincter muscle distinct from the ordinary
endodermal muscle layer of the column, and, consequently, there
is no infolding of the disc in contraction.

The external tentacles are conical, numerous, and entacmez-
ous. They are arranged in five cycles closely crowded together.
The innermost cycle consists of 24 tentacles, as does also the
next external, the third of 48, the fourth of 96, and the fifth of
192; the third and fourth cycles being much crowded together,
so as to look like one. Upon the inner faces of each of the
tentacles are three or four transverse ridges which dilate into
tubercles at either extremity, and are due, as sections show (PI.
IV., Fig. 8) to an increased thickness of the mesogloea in these
regions. Lesueur (17), in his brief description of this form,
notes that “the tranverse tubercles are enlarged at their extrem-
ities, sometimes bilobated”’; and I observed a tendency towards
bilobation in some of my specimens. In Klunzinger’s specimen
of P. loligo (77) the tentacles are “recht und links von der
Mittellinie, mit kleinen rundlichen Warzen besetzt, die oft durch
Querwiilste jederseits verbunden sind, wodurch sie wie gefie-
dert sind. Andermal sind sie zu unregelmassigen Lappchen
oder Gruppen verbunden wie Ehrenberg zeichnet.” The latter
forms approach the Bahaman specimens more than those figured

54 MCMURRICH. [VoL. III.

by Klunzinger, and show an intermediate stage in the com-
plication of the mesogloeal enlargements, the Bahaman forms
representing the simplest stage; while the form mentioned by
Klunzinger in a foot-note, the P. pzunulatum, Martens, from
Singapore, a specimen of which is in the Berlin Museum, rep-
resents the most complicated condition, the pinnulation being
even more marked than in Klunzinger’s figures.

The tentacles of the disc are small wart-like structures, whose
structure is shown in Pl. IV., Fig. 11. Lesueur (?17) describes the
tentacles as perforated warts; but I was not able to distinguish
any trace of a pore inmy sections. The ectodermal muscle layer
of the disc is not very strong, the nerve layer (z), as in the ten-
tacles, being well marked. The ectoderm is raised into numer-
ous elevations, as may be seen from Fig. 11, ec, the mesogloea
not taking part in their formation.

The mesenteries are arranged in four cycles, of which the
first consists of 12 mesenteries, which are attached to the stomo-
dceum throughout its full extent; the second, likewise of 12,
has them attached only about half-way down the stomodceum ;
while the third cycle has its 24 mesenteries entirely free and
imperfect. The longitudinal and parieto-basilar muscles are
present, the former being fairly well developed (Pl. IV., Fig. 9)
and limited to the outer two-thirds of the non-reproductive
portion of the mesentery; while the latter, its upper margin
forming a fold upon the surface of the mesentery, is limited to
its lower one-quarter. The inner stomata are present, but I was
unable to determine the presence of any outer one.

All the mesenteries, even the directives, are gonophoric, and
the animals are bisexual. In connection with the testes I ob-
served what seems to be a structure corresponding to the “ fila-
mental organ,” which the Hertwigs (79) have described in
ovaries of certain forms examined by them. From their studies
of Adamsia (Calliactis) they were inclined to consider this pecu-
liar organ a portion of the protoplasm of the ovary; but later,
R. Hertwig (82) found in Corallimorphus rigidus positive proof
of its origin from the endodermal epithelial cells in the neigh-
borhood of the ova. I am not aware that its existence has
hitherto been definitely described in connection with the testes,
though what Jourdan has described (77) as occurring in the
testes of Actznza equina is probably of this nature. Its occur-

No. 1.] ACTINIARIA OF THE BAHAMAS. 55

rence in Phymanthus is consequently interesting. In structure
(Pl. IV., Fig. 10) it is essentially similar to what Hertwig has
described ; 2.¢., it consists of peculiarly modified endodermal
cells which stain deeply, and are consequently very evident in
sections. I am unable to say whether the filamental apparatus
is present in the ovaries likewise of these forms, since all the
specimens examined were males.

This form seems to occur throughout the whole range of the
West Indies. Lesueur (17) observed it at Barbadoes, and
Duchassaing and Michelotti at the same island and also at St.
Thomas. There can be no doubt as to the identity of the forms
described by these authors with that obtained by me in the
Bahamas. A figure is given by Duchassaing and Michelotti
(66) which has apparently been overlooked by Andres. It is
evidently, however, of a contracted specimen, and cannot be
considered a good representation. The animal figured by Ellis
(’67) without description, and named Actinza aster, has never
been sufficiently characterized to permit of identification, al-
though it has been included by many systematic authors in their
review of the Actinians. The description given by Solander
(86) is very meagre, and includes no specific characters; and
Duchassaing and Michelotti (60 and ’66) simply mention it,
without any description. Judging from the figure given by
Ellis, it seems possible that it may be identical with Phyman-
thus crucifer; but the uncertainty of such an identification is
too great to warrant the insertion of the name among the syno-
nyms given above.

Family Phyllactide.
Synon. — Phyllactinz (pars) — Verrill, 1868.

Stichodactylinze provided with tentacles of two kinds. The
peripheral ones are foliose (fronds), while those towards the
centre of the disc are simple and conical.

Genus Outactis, M.-Edw. and H.

Synon. — Actinia (pars) — Lesueur, 1817.
Metridium (pars) — Dana, 1849.
Actinostella — Duchassaing (teste, Andres).
Oulactis — Milne-Edwards and Haime, 1851.

56 McMURRICH. [Vov. III.

Phyllactidz with the column provided with longitudinal rows
of verrucz in its upper part. The foliose marginal tentacles
(fronds) not arranged in radial series of different degrees of
development. No sphincter muscle.

It seems probable that Verrill’s genus Lophactis (68) should
be included here, leaving only three genera in the family, viz.,
Phyllactis, Oulactis and Asteractis.

11. Oulactis flosculifera (Les.), Duch. and Mich. (PI. IL,
Fig. 2; Pl. IV., Figs. 12-14).
Synon. — Actinia flosculifera — Lesueur, 1817.
Oulactis flosculifera — Duchassaing and Michelotti, 1860.

Oulactis conchilega — Duchassaing and Michelotti, 1860.
Oulactis foliosa — Andres, 1883.

Andres (83) considered the identification of this form by
Duchassaing and Michelotti with Lesueur’s Actinza floscultfera
to be erroneous, imagining the form described by the last-named
author to be more probably an Evactzs. It seems, however, that
Lesueur’s description, though not as clear as is desirable, agrees
fairly well with this form, his marginal ‘“ rows of tubercles sur-
rounded with small warts’’ being a poor description of the
external fronds. The term O. conchilega is the name given in
the index to the plate of Duchassaing and Michelotti’s paper to
Fig. 7 of Plate VII., which in the text is referred to as O. flos-
culifera.

I obtained a single specimen only of this form, buried in sand
up to the tentacles on the shore of the island of New Providence.
It has been found also at Green Turtle Cay, Abaco Island, and
Lesueur’s specimens were obtained at St. Thomas, where it is
found not only in sand, but also in the crevices of the rocks.

In my specimen (Pl. II., Fig. 2) the column was of a delicate
orange-yellow below, shading off above into cream-white, the
verrucze of the upper part being pure white, and the insertions
of the mesenteries showing through as white lines. The fronds
were brown and the tentacles clear translucent white, with
some opaque white spots, elongated transversely on their inner
surfaces. Uhtoff’s drawings of the specimens seen at Green
Turtle Cay represent a somewhat different coloration. They
are much lighter, the column being translucent white with only
a very faint yellowish tinge, the insertions of the mesenteries

No. 1.] ACTINIARIA OF THE BAHAMAS. Wi

showing through, and instead of becoming paler above it darkens
rapidly, and in the region of the verrucz is a very decided brown.
The fronds are yellowish white, and thus very different from
those of the New Providence form, whereas the inner tentacles
are of the same color as in that specimen. The description of
the coloration which Lesueur (17) gives agrees with that of my
specimen. It is as follows: the ‘margin and centre of the
disc and tubercles (z.e. fronds) of an umber color, tentacula of
the same color but paler, furnished with several oblong white
spots, with a blackish brown point in the centre of each spot.”
On the other hand, Duchassaing and Michelotti’s specimens
(60) are apparently markedly different from any of the others.
I quote their description, so far as it refers to the coloration,
verbatim: “ Le corps a une couleur verte disposée en lignes ou
zones longitudinales.”” ‘Le disque est verdatre; les tentacules
d’un jaune clair.”

I do not think it necessary to consider these various forms
distinct species, but prefer to group them together as color
varieties, three such being distinguishable. The predominating
colors of these are:

Var. a. White, becoming darker above, fronds yellowish
white.

Var. B. Yellow, fronds brown.

Var. y. Greenish.

The size and shape of the column varies considerably, accord-
ing to the amount of expansion. When moderately expanded
(Pl. II., Fig. 2) it is cylindrical, and measures 8.9 cm. in height
and 4.4 cm. in diameter; but when fully expanded, becomes
much flatter and broader, assuming the form represented in
Pl. VII, Fig. 7, of Duchassaing and Michelotti’s paper (’60).
It is marked with longitudinal invections, and towards the upper
part is furnished with several longitudinal rows of verrucz, to
which particles of shells, sand, etc., adhere. There is no special
sphincter muscle, the transverse musculature of the column,
although fairly well developed below, becoming obsolete above.
Consequently the tentacles are not infolded in contraction. The
mesoglcea of the column is raised on its outer surface into numer-
ous irregular elevations (Pl. IV., Fig. 12), throwing the ectoderm
into numerous folds. The endoderm is comparatively thin, and
contains numerous “yellow cells.”

58 MCMURRICH. Vor. ULE:

The fronds, situated on the periphery of the disc, are in a
single cycle, one surmounting each longitudinal row of verrucz,
there being altogether apparently 24, corresponding thus to the
intramesenterial spaces. In structure they are irregularly lobed
thickenings of the disc, the mesogloea being thrown into nume-
rous folds, and here and there thickened so as to form slight
wart-like prominences. They lack the folded muscular layer
which is to be found in the disc and in the inner tentacles.
These are situated near the mouth, a naked area of the disc
being left between them and the fronds. I am not quite certain
as to the number of these inner tentacles; I counted 42, but
probably the number should be 48, one corresponding to each
intermesenterial, and one to each intramesenterial space, or else
two to each intramesenterial space, their arrangement not having
been made out. They are cylindrical in shape, tapering towards
the extremity. Their longitudinal musculature is strong (PI. IV.,
Fig. 13, mp), the mesogloea being thrown into numerous ridges,
over which the muscle cells are arranged.

The disc is structurally like the inner tentacles. The mouth
I could not see, the tentacles completely covering it, but pre-
sumably the gonidial angles are well marked. In transverse
sections through the stomodzum the two gonidial folds are
well seen. They extend downwards for some distance, forming
two strong languettes (Pl. IV., Fig. 14). Their structure differs
noticeably from that of the rest of the stomodzeum, the meso-
gloea being much thickened, the ectoderm much higher than
elsewhere, and the nerve layer very distinct. They approach
much nearer the column wall than the stomodzum elsewhere
does, the gonidial groove being very deep.

The pairs of mesenteries are 24 in number, and _ probably
represent ‘three’ cycles, the formula for which 4s, 6, 16, ‘12.
All are perfect. Owing to the depth of the gonidial groove
the directives are much shorter than the other mesenteries.
In all the muscular layers are exceedingly well developed. The
inner mesenterial stomata are present, and the mesenteries of
the third cycle only appear to be gonophoric. The specimens
examined had only male organs.

Now i] ACTINIARIA OF THE BAHAMAS. 59

Tribe EDWARDSI.

« Actiniaria with eight septa; among which are two pairs of
directive septa, whilst the remaining four septa are not paired ;
all the septa furnished with reproductive organs; tentacles
simple, usually more numerous than the septa.” (R. Hertwig
’82.)

I was not successful in obtaining any forms belonging to this
tribe, though they undoubtedly occur in the Bahamas. Dr. H.
V. Wilson informed me that during his stay at New Providence,
which terminated at the time of my arrival, he obtained several
young Edwardsias in the tow-net. This method of collecting I
did not follow very systematically, and amongst the material
brought in found no Edwardsiz,

Tribe ZOANTHEA.

Actiniaria provided with paired mesenteries, each pair con-
sisting of a large perfect macroseptum and a small imperfect
microseptum, except in the cases of the two pairs of directives, one
of which, the dorsal, consists of two microsepta, and the other,
or ventral, of two macrosepta. In some forms the second pair
of septa from the micro-directives on each side consists of two
macrosepta. Each pair is provided with transverse muscles
on the faces turned toward each other, except the directives,
in which the muscles are on the faces turned from each other.
The increase in the number of the mesenteries takes place by
the formation of new pairs in the interspace on either side of
the ventral directives.

Family Zoanthidz.

Zoanthee, in which the individual polyps are usually united
into colonies; the various individuals being either connected
by stolon-like canals or by a common expansion (coenenchyma),
with the endodermal cavities of which the cavities of the polyps
unite.

Cuvier (’’98) was the first to separate the Zoanthids from the
other Actinians, defining the group as consisting of forms “ qui
ont la bouche et les tentacules comme les Actinies, mais dont le

60 MCMURRKICH. [Vot. III.

corps est plus gréle par en bas que par en haut; ce qui leur
donne absolument l’air d’une fleur portée sur un pédicule.” He
places in the group Actinoloba dianthus and Z. sociata, the latter
of which only belongs to the group as now limited. Later,
Cuvier (17) made the formation of colonies the characteristic
feature of the group. Ehrenberg ('34) established a definite
family for the group, naming it Zoanthine and making it equiv-
alent to-all the other forms which constituted the family Acti-
nine. This arrangement was retained byvariousauthors; Gosse,
however (60), separated the Actinaria, with which he associated
the corals, into four tribes, viz.: Astraeacea, Caryophyllacea,
Madreporacea and Antipathacea. The first of these contained
the majority of the Actinians, the Zoanthidz and Capneas, how-
ever, being relegated to the second group, which also contained
the Turbinolidz, Oculinidez, and some other families of corals.

In 1867 Gray ('67) divided the Zoanthinz into two sub-groups,
separating from the fleshy forms those with incrustations of for-
eign material, forming of the latter the sub-group Zoanthini paly-
theine. Verrill (68) recognized the necessity for a more per-
fect subdivision of the Zoanthids, and raised the group to the
dignity of a sub-order, the Zoanthacez, still equivalent, how-
ever, to the rest of the Actinians, and including the families
Zoanthidz, Bergidz, and Orinidez, holding doubtful the pro-
priety of establishing a fourth family for the separate attached
forms which had been described under the generic name /saura,
(Savigny) and H/ughea (Lamouroux.) Sphenopus he considered
related to the Edwardsians, and hence did not take it into con-
sideration. Verrill’s arrangement marks an epoch in the classi-
fication of the Zoanthids, his families Zoanthidz and Bergidze
being equivalent to the same groups as now defined, although
the Orinidze (which includes a single species of Orzzza described
by Duchassaing and Michelotti (60) ) probably does not belong
to the sub-order at all, but contains a form related perhaps to
some of the deep-sea forms, with pores instead of tentacles,
which were obtained by the “ Challenger.”

Klunzinger’s arrangement, so far as it goes, does not present
any advance on Verrill’s, but Hertwig (82), having discovered
the peculiar arrangement of the mesenteries of Zoanthids, Cerian-
theze and Edwardsiz, makes of them three tribes, each equiva-
lent to the Hexactinize, which includes the majority of the remain-

No. 1.] ACTINIARIA OF THE BAHAMAS. 61

ing forms. He recognizes two families in the tribe Zoanthez,
the Zoanthidze and the Sphenopidz. Andres’ classification
(83) is not so advanced as that of Hertwig, since he makes
the family Zoanthinze equivalent to the sub-tribes of the Hex-
actiniz as here recognized.

I would recommend an arrangement combining those of
Hertwig and Andres. I would recognize Hertwig’s tribe
Zoantheze and its equivalency to the Cerianthez, etc., and
assign to it the three families given by Andres, viz.: the
Zoanthidz, the Bergidz, and the Sphenopidz.

Genus ZOANTHUS (Cuv.), Erdmann.

Zoanthidz with fleshy walls, there being no sand or foreign
matter imbedded in the mesogloea; the coenenchyma is stolon-
like, with a slight tendency to form plate-like expansions. The
mesenteries are arranged on the microtypus, and the sphincter
muscle is imbedded in the mesogloea and is double.

The synonymy of this genus, as indeed that of all the genera
of the Zoanthidze, is very much confused, and instead of giving
it in full, I have thought it better to present in a concise form
the limitations of the genus as given by the principal author-
ities.

I. Actinians united in considerable numbers on a common
base — Cuvier (’17), Gosse (60).

II. Actinians with the individuals united by stolon-like pro-
longations — Lesueur (17), Ehrenberg (34), Dana ('46), Milne-
Edwards (57), Duchassaing and Michelotti (60), Gray (67),
Verrill (68), Hertwig (82).

III. Colonial actinians with fleshy walls — Klunzinger ('77),
Andres (’83).

IV. As defined above — Erdmann (85).

The arrangement of the mesenteries in Zoanthus was first ac-
curately made out by R. Hertwig (83), and his results were later
confirmed by G. Miiller (84), Erdmann (85), and W. Koch ('86).
Erdmann, however, first made this arrangement, taken in con-
nection with the nature of the sphincter, of generic importance,
separating forms in which, like Zoanthus, the second pair of
mesenteries in each side, counting from the micro-directives,
consists of a macro- and a micro-septum, from those in which the

62 McMURRICH. (VoL. III.

corresponding pair, as in Palythoa, consists of two macrosepta.
The former arrangement he terms the microtypus, and the latter
the macrotypus.

12. Zoanthus sociatus (Ellis), Lesueur. (Pl. II., Fig. 3; Pl.
IV., Figs. 15-18.)
Synon. — Actinia sociata— Ellis, 1767.
Zoanthus sociatus — Cuvier, 1817.
Zoanthus sociata — Lesueur, 1817.
Zoanthus socialis — Blainville, 1830 (teste Andres).
Zoanthus Ellisii— Bosc, 1802.
Zoantha nobilis — Duchassaing and Michelotti, 1860.

This is one of the earliest non-European Actinians which has
been described, Ellis having described it in 1767. His descrip-
tion, however, is principally anatomical, and sufficient is not
given to distinguish it from other species of Zoanthus. In the
edition of Ellis’ studies on the Corallines compiled by Solander
(’86) it is suggested that this form may be identical with the
“‘Waterbottles ” described by Hughes in his Natural History of
the Barbadoes, published in 1750. Lesueur (17) employed
Ellis’ name for a species which he characterizes with consider-
able clearness, and there is little doubt but that the form
described below is identical with his species. Duchassaing and
Michelotti (60) describe a form, 7. zodzlis, giving as a synonym
for it Z. soctata (Les.), and stating that their form differs from
Lesueur’s in having the tentacles longer and more numerous,
and of a blue color, instead of yellow ; but it seems probable
that the two are identical, the difference in coloration being
comparatively unimportant. Bosc’s name was applied to the
Actinia sociata of Ellis.

This species was very common at New Providence, growing
in masses as much as 15 cm. in diameter. It seems to be
widely distributed throughout the West Indies, since, if the
synonomy given above be correct, it has been described from
Barbadoes, Dominica, and Guadaloupe. In color (Pl. IL., Fig. 3),
the stolon and lower part of the column is usually flesh-colored,
while the upper part of the column is purplish brown; the
tentacles are the same color as the upper part of the column,
while the disc is bright green, sometimes varying to peacock-
blue or pale bluish green; in many forms there were two tri-

No. 1.] ACTINIARIA OF THE BAHAMAS. 63

angular brown spots upon the disc, each with its apex at the
angle of the mouth, the base resting upon the margin.

The stolons in section (Pl. IV., Fig. 16) are seen to contain a
cavity into which numerous small mesenteries project from the
wall, being arranged as in the body of the polyp. The stolons
are evidently elongations of the column of a polyp; the polyp
becomes as it were very much drawn out in its lower portion,
which becomes attached to the surface of the rock and gives
support to the upper portion, rising up at right angles to it. It
is to be noted that the formation of new polyps by budding does
not take place from the stolon, but from the base of the polyp
proper ; z.e., from the region where the polyp joins the stolon.

The polyps measure from 0.9 cm. to 1.25 cm. in height, and
at the top about 0o.4cm. in diameter, tapering off somewhat
below ; in contraction they are club-shaped. The outside of the
column is covered by a well-marked cuticle (Pl. IV., Fig. 15, cz),
to which foreign bodies, such as diatom frustules, etc., are
attached. This cuticle is no doubt a secretion of the ectoderm
cells (ec), which, in the specimens examined, seem to have
become fused to form a vacuolated layer, in which are numerous
nuclei and strands of granular protoplasm. The mesogloea of
the column wall measures 0.06—0.08 mm. in thickness, becom-
ing, however, thicker above, and presents the usual structure
described by Hertwig (’83) and Erdmann (’85). The endoderm
is thin, measuring only 8y—12, and is densely packed with
“yellow cells.’ The general musculature of the column is
very weak, the muscle cells forming an almost flat layer. The
sphincter is imbedded in the mesogloea and is double, the column
wall in contracted individuals being deeply constricted in that
region between the two portions, as in the form figured and
described by Erdmann. The upper portion is small, and has its
muscle fibres running in many cases obliquely, so that a vertical
longitudinal section does not show them cut across transversely ;
the lower portion is long, extending down the column wall for a
distance of about 5 mm.

The tentacles are arranged in two cycles, and in the larger
polyps number from 44 to 50. Their ectoderm does not possess
the cuticle which occurs on the column, but is ciliated. The
muscle layer is weak, but still somewhat stronger than that of
the column wall. The mesogloea differs from that of column in

64 McMURRICH. (Vou. III.

not containing any enclosures of ectoderm cells, and the endo-
derm is much thicker than elsewhere, and is literally loaded
with “yellow cells.” The disc resembles the tentacles in
structure, but the ectoderm cells are less distinct, more nearly
resembling those of the column, and the mesogloea contains
enclosures of ectoderm cells. The stomodzeal ectoderm has no
cuticle and is ciliated, and the mesoderm, containing enclosures
of ectoderm cells, is thrown into slight longitudinal folds (PI. IV.,
Fig. 18).

The mesenteries are arranged on the microtypus (Erdmann),
and vary in number according to the size of the polyp, equalling
in number the tentacles. The increase in number occurs by
the formation of new pairs on either side of the ventral (macro-)
directives, as has been described for other Zoanthidz by G.
Miiller (84) and Erdmann. The mesogloea is thin, measuring
only about 4; the basal canal is long and not at all wide, pro-
ducing only a very slight basal thickening of the mesentery
(Pl. IV., Fig. 17); and the musculature is weak, forming a single
almost smooth layer covering the whole surface of the mesen-
tery, the mesogloea not being raised into folds to support it as in
the Zoanthus from the Bermudas described by Erdmann. In
one mesentery I observed the basal canal communicating with
one of the spaces in the mesogloea of the column wall. It seems
open to question whether the cells of the larger cavities in the
mesogloea are not in reality endodermal in their origin.

In none of the specimens examined were any reproductive
organs present.

Genus GEMMARIA (Duch. and Mich.).

Synon. — Gemmaria — Duchassaing and Michelotti, 1860.
Epizoanthus (in part) — Verrill, 1868.

Zoanthidz with sand or foreign matter imbedded in the meso-
gloea; the coenenchyma is absent or lamellar; the mesenteries
are arranged on the microtypus, and there is a single sphincter
enclosed in the mesoglcea.

An arrangement such as is described in the above definition
is not included among those given by Erdmann (85), and I have
consequently referred the single form which possesses it to a
distinct genus to which I have applied Duchassaing and Miche-

No. I.] ACTINIARIA OF THE BAHAMAS. 65

lotti’s name Gemmaria, since in its general characters the form
to be described seems to resemble not a little their Gemmaria
Ruzet, though differing decidedly from it in coloration. The
forms included in the genus as here defined approach £fzzoan-
thus, but differ in not incrusting shells, etc., and in having the
mesenteries arranged on the microtypus.

13. Gemmaria isolaia, n. sp: (PL 11.) Fig. 4; Pl TV., ‘Figs:
19-20.)

I met with this species on a single occasion only, while col-
lecting at the eastern end of Rose Island. The individuals
were scattered and buried up to the tentacles in sand. Owing
to the depth of the water and the rapid tide I was unable to
observe the coenenchyme, and it is quite possible that the ani-
mals may be solitary, though I am inclined to believe that they
are connected by a thin continuous lamellar coenenchyme. A
single individual has a bud arising from its base.

The column is cylindrical, broader above than below. In
height it measures 2.5 cm., the disc when expanded measuring
about 0.8 cm. in diameter. In color the column (PI. II., Fig. 4)
is grayish yellow, owing to the incrusting matter. The disc and
tentacles are ochre-yellow, the latter being spotted with white
on their inner surfaces. The peristome and mouth are white.

The ectoderm is protected by a not very strong cuticle, and
is composed of several rows of cells, presenting an appearance
similar to that figured by Erdmann for Zoanthus. It measures
0.024-0.04 mm. in thickness. The mesogloea contains en-
closures of foreign bodies —'sand, foraminifera and radiolarian
shells, and sponge spicules —almost throughout its entire thick-
ness, but towards the upper part these foreign substances are
less abundant and are confined to a greater extent to the outer
region of the mesogloea. This layer is about 0.4 mm. in thick-
ness. The sphincter is single and imbedded in the mesoglcea,
in its upper part being about half-way between ectoderm and
endoderm, but lower down approaching the endoderm so as to
be separated from it only by a thin layer. Above it consists of
a single row of cavities, few in number, containing muscle cells,
arranged in various directions, so that many are cut obliquely ;
but below (Pl. IV., Fig. 19) it consists of a single row of circu-

66 MCMURRICH. [VoL. III.

lar cavities, apparently without any muscle fibres and with a
darkly staining border.

The tentacles are rather short and somewhat acuminate, and
are arranged in two cycles, there being from 31 to 34 in each
cycle. The disc has its mesogloea densely loaded with enclosed
cavities, containing cells probably ectodermal and muscular in
their nature (Pl. IV., Fig. 21). The stomodzum (PI. IV., Fig.
20) is peculiar in being rounded at its dorsal edge, but abruptly
truncated at the ventral or gonidial edge, the directives being
attached one to each angle formed by the truncation.

The mesenteries are arranged on the microtypus and are very
slender, the musculature being only slightly developed and ar-
ranged as in Zoanthus sociatus. The basal canal in many cases
forms a circular cavity similar to those forming the greater por-
tion of the sphincter, but in the majority of cases is slender and
produces only a slight enlargement of the base of the mesen-
tery. None of the specimens examined possessed reproductive
organs.

Genus CoRTICIFERA (Les.), Erdmann.
Synon. — Palythoa auct.

Zoanthidz, with sand or foreign matter imbedded in the
mesogloea, and the polyps imbedded throughout their greater
extent in ccenenchyma ; sphincter muscle single enclosed in the
mesoglcea ; mesenteries arranged on the microtypus.

This term was first proposed by Lesueur (’17) for the recep-
tion of the Zoanthidz, in which the polyps were imbedded
nearly to the tentacles in a coenenchyma. Later the term
Palythoa was limited so as to include forms with this character-
istic (Verill 68 and Gray ’67), and Lesueur’s term passed out of
use, but has been revived again by Erdmann (’85).

14. Corticifera flava, Les.

Synon. — Corticifera flava — Lesueur, 1817.
Palythoa (Corticifera) flava — Duchassaing and Michelotti, 1860.
Palythoa mammillosa, var. flava — Duchassaing and Michelotti, 1866.

This form was very abundant at New Providence, forming
colonies of from 15—22.5 cm. in length by from 7.5-12.5 cm. in
breadth in the shallow water along the shores. I identify it

No. 1.] ACTINIARIA OF THE BAHAMAS. 67

with Lesueur’s Corticifera flava (’17) with tolerable certainty. I
was inclined for a time to consider it identical also with the
form described by Ellis and Solander (86) under the name
Alcyonium mammillosum, but there is too much uncertainty
regarding this form. Dana (46) and Milne-Edwards (’57) be-
lieve this to be a form in which the polyps project somewhat
above the surface of the coenenchyma, a conclusion no doubt
derived from the figure given by Solander. I think, however,
it would be as well to allow Ellis and Solander’s name to lapse
altogether, since the description which they give is not suffi-
cient to allow of certainty in the identification of any form with
it, and has already given rise to some confusion.

Andres identifies Lesueur’s species with Klunzinger’s Paly-
thoa tuberculosa (77) from the Red Sea. Miiller (84) has
described the arrangement of the mesenteries of this form, and,
as will be seen, it differs in some respects from the Bahama
form. Erdmann, too (85), has given a brief description of a
form from Simons’ Bay, Cape of Good Hope, which Hertwig
(88) identifies with Klunzinger’s Palythoa tuberculosa, and this
also disagrees in some points, both with Miiller’s description
and with the Bahaman species. It seems doubtful accordingly
if the identifications of Hertwig and Andres are correct.

In C. flava the polyps are deeply imbedded in the ccenen-
chyma and are separated from each other by slight intervals of
that tissue, so that their outline is circular and not polygonal
from mutual pressure, as in Hertwig’s C. tuberculosa. In pre-
served and therefore contracted specimens the height of the indi-
vidual polyps is about 1.5 cm. and the breadth 0.5 cm., agreeing
in this respect with Miiller’s form, but differing from Hertwig’s,
the measurements of:which are respectively 6-8 mm. and 5
mm. In the expanded condition the disc of C. flava measures
0.8 cm. in diameter. The small portion of the polyps which
extend above the coenenchyma forms in preserved specimens a
ring-like swelling, the surface of which is marked with radiating
furrows, which in expanded individuals may be seen to extend
to the margin, separating there 16-18 tubercles. This character
seems to be possessed also by Klunzinger’s and Hertwig’s forms,
and this appears to have been the principal reason for the
fusion by Andres of Lesueur’s and Klunzinger’s species.

The basal member of the coenenchyma is not particularly

68 MCMURRICH. [Vou. III.

thick, but is of smaller extent than the upper surface of the
colony ; in consequence of this the polyps towards the periph-
ery of the colony approach more or less a horizontal posi-
tion.

The ectoderm of the polyps is protected by a cuticle, and
consists of several rows of cells as in Gemmaria isolata and
the Zoanthus from the Bermudas described by Erdmann. The
mesoderm is thickly studded with imbedded foreign substances,
such as grains of sand, foraminiferal and radiolarian shells, and
sponge spicules, a thin layer only, adjacent to the endoderm,
being free from these bodies. Neither Hertwig nor Erdmann
makes any definite statement regarding the arrangement of
these imbedded particles in their C. tuderculosa, merely stat-
ing that in its anatomical characters it agrees with the Ber-
muda form which Hertwig identifies with Quoy and Gaimard’s
P. lutea. In this the foreign particles are limited to a small
region of the mesogloea immediately below the ectoderm and to
the coenenchyma between the polyps, being here scattered ; else-
where the mesogloea is soft. I was not able to detect in the
Bahama form any of the definitely shaped calcareous bodies
with a radiating structure which Miiller and Klunzinger de-
scribe as occurring in P. tuberculosa and which remind one of
Alcyonarian spicules.’ The mesogloea, as in other Zoanthide,
contains numerous endodermal canals and isolated ectodermal
cell-islands as well as the connective tissue cells. The sphinc-
ter resembles closely that of Gemmaria, differing from it only
in that there are a greater number of spaces filled with muscle
cells towards its upper end.

The margin of the polyps, as stated above, is tuberculate, the
tubercles varying in number from 16-18. The tentacles vary
in number, the largest polyps possessing 36-40 arranged in two
cycles. The disc is concave, and the peristome elevated and
provided with minute white tubercles. The stomodzeum resem-
bled that of Gemmaria in shape. (See Pl. IV., Fig. 20.)

The mesenteries are arranged on the microtype, and were
delicate with weak musculature. Unfortunately, the material I
brought back with me was not preserved sufficiently well to
allow a study of the histology of the internal parts. I did not
observe any reproductive organs in the forms examined. Miil-
ler states that in P. ¢uberculosa the mesenteries unite at the

No. 1.] ACTINIARIA OF THE BAHAMAS. 69

base of the polyp to form a more or less retiform tissue. This
does not seem to be the case in the Bahama form. The endo-
derm of the mesenteries is pigmented.

The entire colony was of a sandy yellow color, the disc being
darker, verging towards brown.

Tribe CERIANTHEA.

Actiniaria with numerous unpaired mesenteries and a single
ventral gonidial groove; the mesenteries are longest on the
ventral side and diminish gradually towards the dorsal aspect ;
the two mesenteries attached to the bottom of the gonidial
groove (the directives) are remarkably small, and are distin-
guished in this way from the other ventral septa (Hertwig).

I was not successful in obtaining any members of this tribe,
but Dr. H. V. Wilson discovered several free-swimming larvz
belonging apparently to a species of Cereanthus.

- I wish to add a few remarks of a general nature which have
been suggested by the studies, the results of which are given
in the preceding pages.

I was much struck by the resemblance which the Actiniarian
fauna of the Bahamas presents to that of the Pacific, and its
decided difference from that of the eastern coast of America.
It must be granted of course that little is known regarding the
Actinology of the Gulf of Mexico and of the Central and South
American coasts, but on the other hand the Actinians occurring
on the Atlantic coast of the United States as far south as
Charleston, S. C., are well known, and the dissimilarity of the
Bahama forms to these is very apparent. To make a generali-
zation, we may say that the Actinian fauna of the Pacific differs
from that of the Atlantic in the greater number of Stichodacty-
linze and Thalassianthinz which it contains, and the number of
forms of the former sub-tribe occurring in the Bahamas is very
noticeable. It seems that so far as the Actiniaria are concerned
two great areas of distribution can be defined, —the Indo-Pacific,
including the Indian and Pacific oceans and the seas connected
with them, such as the Red Sea; and the Atlantic, including in
this the Mediterranean. The Caribbean region of the Atlantic
is, however, to be separated from the Atlantic region and united

7O McMURRICH. (Vou. III.

with the Indo-Pacific, the relationships of its Actiniaria being
very certainly with those of that region. How far this may
hold in the case of other animal groups remains to be seen, and
to enter into the question fully would be beyond the scope of
this paper. It may be noted, however, that von Lendenfeld, in
a recent paper! states that the Fibrospongiz of the Atlantic
region of North America (from the context I presume he means
more especially the West Indian region) and of the East African
region are most nearly related to the Australian forms. He
also states, however, that there is more similarity between the
North American and Australian forms of this group, than be-
tween those of the latter region and those of the northeastern
portion of the Indian Ocean.

Of the tribe Hexactiniz the sub-tribe Actininz has represen-
tatives in both regions, and the similarity in genera is quite evi-
dent. The Stichodactylinz are, however, much more abundant
in the Indo-Pacific (including in this the Caribbean region) than
in the Atlantic. Of the families of this tribe the Corynactide
occurs in both regions, and the Aurelianidz in the Atlantic
region only, unless the Actinoporus elegans of Duchassaing and
Michelotti (60) and the Actinza osculifera of Lesueur (17),
which occur in the West Indies, are, as Andres thinks, Aure-
lians. This seems very doubtful, however. The other families,
Discosomidz, Rhodactide, Phymanthidz, Phyllactide, Cram-
bactidz, and Criptodendride, are unrepresented in the Atlantic
region (excluding the Caribbean area), and of these all but the
last two are represented in the West Indies. The similarity of
many of the West Indian genera to those of the Red Sea is
especially remarkable. Thus Dzscosoma anemone is most nearly
related to D. giganteum of Klunzinger. The only two species
of Rhodactis known, R. rhodostoma and R. Sancti Thome, occur
respectively in the Red Sea and in the West Indies ; Heteran-
thus floridus is closely related to Klunzinger’s H. verruculatus ;
and of the Actininz, Condylactis passiflora is related to Klun-
zinger’s Paractis erythrosoma.

The only forms found by me at the Bahamas which are char-
acteristically Atlantic, are the Aiptasias, Bunodes tentatus and
Aulactinia stellordes.

IR. von Lendenfeld.— Der Charakter der australischen Célenteratenfauna.
Biolog. Centralbl., V11., 1887-88.

Mp... 2..] ACTINIARIA OF THE BAHAMAS. 71

The occurrence of Lebrunea neglecta in shallow water in the
West Indies is of considerable interest in view of the fact that
the other members of the sub-tribe Dendromeline, so far as is
known, occur in deep water — 2160 and 1375 fathoms — off the
coast of Chili. I think there can be little doubt but that Hert-
wig’s Ophiodiscz are related to Lebrunea in the possession of the
peculiar pseudotentacles ; and this being the case, we have two
related genera, the only ones known of the family, living under
conditions apparently totally different. Ophzodiscus lives in a
region in which prevail absolute darkness, almost total stillness,
and a comparatively very low temperature, whereas Lebrunea
is exposed to the full light of the sun, to water constantly in
motion, and to a perennially high temperature. This seems at
first sight to be a decided anomaly, but I think an explanation
is to be found in a suggestion made by Semper.! He has shown
that a great number of genera of Holothuridz, which were gen-
erally supposed to be boreal, living at considerable depths in
northern seas, occurred in the Philippines, and only at a mod-
erate depth. The conclusion follows that it is not so much the
absolute temperature which limits the distribution of animals as
the exposure to great or more or less sudden variations, Al-
though the absolute temperatures to which Ledrunea and Ophio-
discus are exposed differ enormously, yet in both cases it is an
equable temperature, an almost constant great degree of cold in
the case of the latter, while Ledrunea lives in the warm waters
of one of the most equable climates known.

To return to the question of distribution, I think that the rela-
tionships of the West Indian Actiniaria to those of the Pacific is
another piece of evidence in favor of a past communication be-
tween the Atlantic and Pacific oceans through the Isthmus of
Panama. It is a case in accordance with what is known regard-
ing the similarities in the fishes, mollusca, and Holothurians of
the two sides of the Isthmus.

November 21, 1888.

1C, Semper, Reisen im Archipel Philippinen. Theil II., Bdi. “ Holothurien.”
Wiesbaden, 1868.

McMURRICH. [Vot. III.

BIBLIOGRAPHY.

J. Ellis. Ax account of the Actinia Sociata or Clustered Animal flower,
lately found on the Sea-coasts of the newly ceded Islands. Phil.
Trans: LV il., 1767.

Pet. Forskal. Descriptiones animalium, que in itinere orientale ob-
servavit, P. F. UHafnix. 1775-6.

J. Ellis and D. Solander. The natural history of many curious and
uncommon Zoophytes, etc. London. 1786.

J. F. Gmelin. In Linneus’ Systema nature, Edit. XITI. Lipsie.

1788-93.
G. L. Cuvier. Tableau élémentatre de Vhistotre naturelle des Animaux.
Paris. 1798.

L. Bosc. Héstotre naturelle des Vers. Paris. 1802.

J. V. Lamouroux. //istoire des Polypiers coralligines flexibles vulgaire-
ment nommeées Zoophytes. Caen. 1816.

G. L. Cuvier. Le Régne Animal. Paris. 1817.

C. A. Lesueur. Observations on several species of Actinia. Journ.
Acad. Nat. Sci. Philadelphia. I. 1817.

R. P. Lesson. Zoologie, in Voyage autour du monde sur la corvette de
S. WM. la Coquille, pendant les années 1822-25 par L. F. Duperry.
Paris. 1828.

S. Leuckart. In Ruppel’s Rese in nordlichen Africa. Frankfurt.
A/M. 1828.

H. M. Blainville. Zoophytes, in Dictionnaire des Sciences naturelles.
Ws 2836:

C. G. Ehrenberg. Dze Coraillthiere des Rothen Meeres. Berlin. 1834.

G. P. Deshayes. In Lamarck’s “Histoire naturelle des Animaux sans
vertébres. Bruxelles. 1837-39.

J. D. Dana. Zoophytes, in United States Exploring Expedition during
the years 1838-42. The atlas was published in 1849.

H. Hollard. Monographie anatomique du genre Actinia. Ann. des
Sci. Nat., 3™¢ Série. Zoologie. XV. 1851.

J. Haime. Observations sur quelques points de Jl organisation des
Actinies. Comptes Rendus. XXXIX. 1854.

H. Milne-Edwards. Histoire Naturelle des Coralliaires ou polypes
proprement dits. Paris. 1857-60.

P.H.Gosse. Ox the British Actinig. Ann. Mag. Nat. Hist. 3d Series.
P1858.

Duchassaing and Michelotti. J¢émoire sur les Coralliares des Antilles.
Mem. Reale Accad. di Torino. Sér. 2™:. XIX. 1860.

P. H. Gosse. A History of the British Sea-Anemones and Corals, or
Actinologia Britannica. London. 1860.

A. E. Verrill. Revision of the Polypi of the Eastern Coast of U. S.
Mem. Boston Soc. Nat. Hist. I. 1866-69. Paper published in 1864.

No. 1.]

ACTINIARIA OF THE BAHAMAS. 73

66. Duchassaing and Michelottis Supplément au Mémoire sur les Coral-

66.
167.

68.

82.

83.
84.

85.

86.

88.

A.

laires des Antilles. Mem. Reale Accad. di Torino. Sér. 2™e,
XXIII. 1866.

E. Verrill. Synopsts of the Polyps and Corals of the North Pacific
Exploring Expedition. Comm. Essex Inst. V. 1866.

J. E. Gray. Votes on Zoanthina, with descriptions of some new genera.

>

ac)

OO

Proc. Zool. Soc. London. 1867.

. E. Verrill. Review of Polyps and Corals of the West Coast of

America. Trans. Connecticut Acad. I. 1866-71.

. Fischer. Recherches sur les Actinies des cotes octaniques de France.

Nouv. Arch. du Muséum. X. 1875.

von Heider. Sagartia troglodytes, Gosse. Ein Beitrag zur Anatomie
der Actinien. Sitzungsber. der K. Acad. Wien. LXXV. 1877.
B. Klunzinger. Die Korallthiere des Rothen Meeres. 1* Theil.
Alcyonarien und Malacodermen. Berlin. 1877.

and R. Hertwig. Dze Actinien anatomisch und histologisch mit
besonderer Bertcksichtigung der Nervenmuskelsystems untersucht.
Jenaische Zeitschr. XIV. 1879.

Hertwig. Report on the Actiniaria, in Reports on the Scientific
Results of the Voyage of H. M. S. Challenger during the years
1873-76. Zoology. VI. 1882.

. Andres. Le Aétinie. Fauna und Flora des Golfes von Neapel.

IX Monographie. 1883.
Miller. Zur Morphologie der Schetdewiinde bei einigen Palythoa
und Zoanthen. Inaug. Dissert. Marburg. 1884.

. Erdmann. Ueber einige neue Zoantheen — Ein Beitrag zur anatomt-

schen und systematischen Kenntniss der Actinien. Jenaische Zeit-
schr. XIX. 1885.

W. Koch. Meue Anthozoen aus dem Golf von Guinea. Marburg.

R.

1886.

Hertwig. Supplement to Report on Actiniaria, in Reports of the
Scientific Results of the Voyage of H. M. S. Challenger during the
years 1873-76. Zoology. XXVI. 1888.

74 MCMURRICH.

EXPLANATION OF PLATES.

D & D!= directive mesenteries. nm = nerve layer.
ec = ectoderm. ~6m = parieto-basilar muscle,
en = endoderm. s¢ = stomodzeum.
go = gonidial groove of stomodzum. sp = sphincter muscle.
nt = muscle cells. ¢= tentacle.
mec = modified ectoderm. ver = verruca.
mel = elevations of mesogloea. yc = yellow cells.
mes = mesentery. I., II., III., I1V., V.= the cycles of mesen-
mgl = mesoglcea. teries.

mp = muscle processes of mesogloea.

DESCRIPTION OF PLATE I.

(All the figures are natural size.)

Fic. 1. Aiptasia annulata (Les.), And.

Fic. 2. Aiptasia tagetes, var. a, spongicola.

Fic. 3. Condylactis passiflora, Duch. and Mich.
Fic. 4. Bunodes teniatus, n. sp.

I
2
3
4
5: Aulactinia stelloides, n. sp.
Fic. 6. Sextant of disc of Audactinia stelloides.

7. Lebrunea neglecta, Duch. and Mich.

8. Discosoma anemone (Ellis), Duch.

9. Rhodactis Sancti Thome (Duch. and Mich.).

0. Heteranthus floridus (Duch. and Mich.)

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DESCRIPTION OF PLATE II.

(All the figures are natural size.)

Fic. 1. Phymanthus crucifer (Les.), And.

Fic. 2. Oulactis flosculifera (Les.), Duch. and Mich., partly expanded.
Fic. 3. Zoanthus sociatus (Ellis), Les.

Fic. 4. Gemmaria isolata, n. sp.

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78 McCMURRICH.

DESCRIPTION OF PLATE III.

Fic, 1. Transverse section of directive mesentery of Aipfasia annulata. X 30.

Fic. 2. Transverse section of mesentery of I. cycle of Aiptasia tagetes. X 44.

Fic. 3. Diagrammatic transverse section of column of Azf/asia tagetes, showing
the arrangement of the mesenteries.

Fic. 4. Longitudinal section of the upper part of the column of Condylactis passt-
flora, showing the absence of a special sphincter. X 50.

Fic. 5. Portion of a transverse section of a contracted tentacle of Condylactis
passiflora. X 185.

Fic. 6. Portion of a transverse section of a mesentery of Condylactis passifiora,
showing the arrangement of the mesoglceal muscle processes. X 60.

Fic. 7. Transverse section of the sphincter muscle of Bunodes teniatus. X 45.

Fic. 8. Longitudinal section of column wall of Ax/actinia stelloides, passing
through two verrucal tubercles. X 52.

Fic. 9. Transverse section of sphincter muscle of Au/actinia stelloides. X 60.

Fic. 10. Diagrammatic transverse section of a sextant of the column of Aulac-
tinia stelloides, to show the arrangement of the mesenteries.

Fic. 11. Pseudo-tentacle of Ledrunea neglecta, expanded. Natural size.

Fic. 12. Transverse section through the basal portion of the pseudo-tentacle of
Lebrunea neglecta. X4l.

Fic. 13. Transverse section through a tentacle, towards its tip, of Ledrunea
neglecta. X 114.

Fic. 14. Transverse section through basal portion of mesentery of Ledrunea
neglecta. X72.

Fic. 15. Transverse section of sphincter muscle of Discosoma anemone. X65.

Fic. 16. Longitudinal section through column wall of Dzscosoma anemone, to
show the elevations of the mesogloea. X 83.

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80 MCMURRICAH.

DESCRIPTION OF PLATE IV.

Fic. 1. Portion of transverse section through a mesentery of Discosoma anemone.
X 59-

Fic. 2. Portion of tangential section through disc and column of Rhodactis Sancti
Thome, just below the bases of the marginal tentacles. ex= endoderm of column;
en' = endoderm of disc; ec= ectoderm of disc; ~e= large nematocyst in endoderm.
<H23

Fic. 3. Portion of transverse section through the stomodzum of Rhodactis Sanctt
Thome. X45.

Fic. 4. Portion of transverse section through the body wall of Heteranthus flort-
dus. X 44.

Fic. 5. Longitudinal section through a disc tentacle of Heteranthus floridus.
X 64.

Fic. 6. Transverse section through a verruca of Phymanthus crucifer. py = pyri-
form cells (nerve cells?). XX 50.

Fic. 7. Longitudinal section through the upper portion of the column wall of
Phymanthus crucifer. X50.

Fic. 8. Transverse section through a tentacle of Phymanthus crucifer. mgl= thick-
ened mesoglcea. X 16.

Fic. 9. Portions of transverse section through a mesentery of Phymanthus cru-
cifer: a, near its base; 4, near its middle. X 35.

Fic. 10. Transverse section through gonophoric region of a mesentery of Phy-
manthus crucifer. te= testis; f:=filamental apparatus. X 250.

Fic. 11. Longitudinal section through a disc tentacle of Phymanthus crucifer.
X 100.

Fic. 12. Portion of longitudinal section of column wall of Oudactis flosculifera, to
show elevation of the mesogloea. X 56.

FIG. 13. Portion of transverse section of a tentacle of Oxlactis flosculifera. X72.

Fic. 14. Transverse section through the gonidial groove of the stomodzum of
Oulactis flosculifera. X25.

Fic. 15. Portion of transverse section through the column wall of Zoanthus soct-
atus. cu=cuticle; emc = endodermal canal in mesoglcea. X 265.

Fic. 16. Transverse section of stolon of Zoanthus sociatus. X 30.

Fic. 17. Transverse section of basal portion of macroseptum of Zoanthus sociatus.
bc = basal canal.

Fic. 18. Transverse section of stomodeum of Zoanthus sociatus. X 33.

Fic. 19. Longitudinal section through margin and upper part of column wall of
Gemmaria isolata, showing the sphincter muscle. X 25.

Fic. 20. Transverse section of the stomodzeum of Gemmaria isolata. X 27.

Fic. 21, Radial section of disc of Gemmaria isolata.

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CONTRIBUTIONS TO THE COMPARATIVE OSTE-
OLOGY OF THE FAMILIES OF NORTH
AMERICAN PASSERES.

R. W. SHUFELDT, M.D., C.M.Z.S.

Two years ago, when our Ornithologists’ Union published its
official avifaunal List of American Birds, the Order PASSERES
was made to contain four hundred and thirty-two (432) species
_and sub-species,! which formidable array is therein duly divided
and subdivided into its sub-orders, families, sub-families, genera,
and so on. It would be far exceeding the scope of the present
memoir to present a detailed scheme of the classification adopted
by the Union for this extensive group of birds ; much less would
it be appropriate for the writer to undertake to offer here a
complete list of these forms, giving the name of each species,
as the reader can, by a brief perusal of the work referred to,
soon obtain a comprehensive idea of such matters. As we pro-
pose to deal here with the osteology of the Famriies only, I
present, as a mere matter of convenience, the ORDER below, with
its divisions through those groups; and a glance at this scheme
of the Order, as given, shows us that we have twenty (20) Fam-
ilies of these North American Passeres to be taken into consid-
eration, and it may be as well to add here that the number of
species, however, contained in any single family or group varies
considerably ; and we see, for example, such a family as the
Cinclide represented by but a single species, while, on the other
hand, such a family as the Fringilide contains upward of a
hundred and forty species or more.

1The Code of Nomenclature and Check-List of North American Birds adopted by
the American Ornithologists’ Union. New York, 1886. In this work the term
“North American,” as applied to its List of Birds, is held to include the continent of
North America north of the present United States and Mexican boundary, as well as
Greenland, and the peninsula of Lower California, with the islands naturally be-
longing thereto.

82 SHUFELDT. (VoL. III.

ORDER. SUB-ORDERS, FAMILIES. Includes
Clamatores. 1. Tyrannide. Tyrant Flycatchers.
2. Alaudide. Larks.
3. Corvide. Crows, Jays, and Magpies.
4. Sturnide. Starlings.
5. Icteride. Blackbirds, Orioles, etc.
6. Fringillide. Finches, Sparrows, etc.
7. Tanagride. Tanagers.
8. Hirundinide. Swallows.
g. Ampelide. Waxwings, etc.
Io. Laniid. Shrikes,
: 11. Vireonidee. Vireos.
SS SI \12. Coerebide. Honey Creepers.

13. Mniotiltide. Wood Warblers.
14. Motacillide. Wagtails.

15. Cinclide. Dippers.

16. Troglodytide. Wrens, Thrashers, ete.

17. Certhiide. Creepers.

18. Paride. Nuthatches and Tits.

Ig. Sylviide. Warblers, Kinglets. Gnatcatchers.
20. Turdide. Thrushes, Solitaires, Stonechats,
L Bluebirds, etc.

These Families, then, are presented in the order in which
they appear in the A. O. U. Check-List, and as the systematists
who compiled that work declare that “the List [is] to begin
with the lowest or most generalized type, and end with the
highest or most specialized” (p. 15), it is but fair to presume
that as the families begin with the Zyvannide and conclude
with the 7urdide, the former were considered to be the “most
generalized types,” the latter the “most specialized,” while the
eighteen families, serially arranged between these extremes,
hold their several positions in recognition of this plan.

For the past ten years the present writer has been gradually
collecting together, in various parts of the United States and
from various sources, osteological material illustrative of the
group of passerine birds; so that at this writing we have before
us a very fair representative line of such skeletons. And with
but few exceptions, every family in the above list is in this
way at our hand, and the missing forms are from groups, the
species of which come to us usually only as stragglers, or
casuals, as Sturvnus vulgaris and the Bahama Honey Creeper
(C. bahamensts), but no others.

No. 1.] NORTH AMERICAN PASSERES. 83

It is our aim in the present connection to place before the
reader a brief, concise sketch of the osteology of one or more
species of as many of these passerine families as possible, and
as such work proceeds, compare the salient features of the
skeleton of any family with the corresponding ones as found in
species of another or other family or families supposed to be
more or less nearly affined. Possibly by such means we may be
enabled to point out, so far as skeletal characters are concerned,
the relations that some of the groups of this always puzzling
order to the taxonomist apparently bear to each other, though
no one is better aware than the writer that such complex ques-
tions can never be fully determined until the morphology of
each and a// the species of the Passeres is worked carefully out
in its minutest details, and this we have spoken of again and
again in our published memoirs. It is earnestly hoped that the
work here undertaken may assist matters to that end, and will
to some degree supplement the able endeavors of former authors
in the same field.?

Few ornithologists better appreciate the difficulties which
still stand in the way of a correct classification of the order
Passeres than my friend Professor Newton, and this distin-
guished authority has said that, in referring to this group,
‘‘ Some two or three natural, because well-differentiated, families
are to be found in it, — such, for instance, as the Azrundinide,
or Swallows, which have no near relations; the A/audide, or
Larks, that can be unfailingly distinguished at a glance by
their scutellated planta, as has been before mentioned; or the
Meliphagide, with their curiously constructed tongue. But the
great mass, comprehending incomparably the greatest number
of genera and species of birds, defies any surer means of sepa-
ration. Here and there, of course, a good many individual
genera may be picked out capable of most accurate definition ;
but genera like these are in the minority, and most of the re-
mainder present several apparent alliances, from which we are
at a loss to choose that which is nearest. Four of the six
groups of Mr. Sclater’s ‘Laminiplanter’ Osczmzes seem to pass
almost imperceptibly into one another. We may take examples
in which what we may call the Thrush form, the Tree-creeper

1 McGILLIvRay, W., British Birds, I., pp. 485, 486; and PARKER, W. K., Zrans.
Zo6l. Soc., V., p. 150.

84 SHUFELDT. (Vou. Ill.

form, the Finch form, or the Crow form, is pushed to the most
_ extreme point of differentiation ; here we shall find that between
the two outposts thus established there exists a regular chain of
intermediate stations, so intimately connected that no precise
lines of demarcation can be drawn cutting off one from the
other. 7

Now these observations apply nowhere more cogently than
they do in the study of the osteology of the Passeres, and it is
positively almost beyond the range of possibilities, sometimes,
to distinguish between the skeletons of certain closely related
species, while in other instances very excellent differentiating
characters may be found; and these latter will be brought con-
spicuously into the foreground and made the most of, when
met with. It matters but little which family we select to com-
mence this series of osteological comparisons of this order of
birds, though for convenience’ sake, solely, the writer proposes
to take the genus Szala of the family Zurdzde@ first in order,
because on this occasion it is desirable to follow the sequence
adopted by the A. O. U. Check-List. Not that we are at all con-
vinced that the Zurdide constitute the most highly specialized
group of birds in our avifauna, for we have decided opinions and
leanings quite the converse to any such an hypothesis ; but more
for the reason that we find in such a skeleton as is furnished us
by Szalia a type, as it were, of what we have been given to
understand the passerine skeleton, through the numerous de-
scriptions of a host of former anatomists, purports to be.

We have divided our Yurdide into two sub-families — the
Myadestine and the Turding ; the first containing the genus
Myadestes, and represented by the sole species JZ. townsendiz,
and the second the genera 7urdus, Merula, Hesperocichla, Cyane-
cula, Saxicola, and Szala,—each containing one or more well-
known species of Thrushes or Thrush-like birds.

There are four species of Bluebirds in the genus Sza/za, and I
have compared the skeletons of all. It is hardly necessary to
say that in these several species the skeleton is essentially the
same, although one might, after long and careful study and com-
parison, be enabled to pick out those belonging to the different
varieties. In the most typical species, each seems to possess

1 NEWTON, ALFRED, F.R.S., etc., etc., Article “ Ornithology,” Brit. Encycl., oth
ed., Vol. XVIII, p. 47. 1885.

Wo. 1.) NORTH AMERICAN PASSERES. 85

in its skeleton a faczes peculiar to itself, but often difficult to
satisfactorily describe.

In another connection the writer has already presented a view
of the superior aspect of the skull in Sialia mexicana, so it will
not be necessary to re-describe it here! Upon the lateral
aspect of this part of the skeleton in the Bluebirds, we are to
note the large subelliptical aperture of the external nares,
and the complete absence of any osseous septum between it and
the corresponding opening on the opposite side. The superior
osseous mandible is somewhat curved, tapers smartly to its apex,
and is possessed of cultrate tomia. Standing as a good-sized
bony partition, we have a quadrilateral os plana or pars plana
dividing, as usual, the rhinal chamber from the orbit, while
in nestling specimens of any of the Sza/za, we find in front of
this a large and free lacrymal bone, much as it occurs in the
Corvide ; here, however, this ossicle completely fuses with the
pars plana by the time the bird has fully matured, which is not
the case among the Crows.?

Bluebirds, as is the rule among most, if not all, true 7urdide,
have capacious orbital cavities, with a very deficient bony septum
dividing them. This deficiency is due to a sizable vacuity which
occupies its central part, while the opening for the first pair of
nerves is unduly large, and encroaches to no small degree upon
the upper part of the interorbital septum. Notwithstanding
these facts, in most specimens the foramina rotunda remain
both distinct and entire. Passing to the posterior lower mar-
ginal boundary of an orbit, it is seen that neither the sphenotic
nor the squamosal process in Sza/za is very well developed ; the
latter being rather the better of the two, projecting out as it
does over the mastoidal head of the quadrate on either side.

1 SHUFELDT, R. W., “Notes upon the Osteology of Cinclus mexicanus” #z//.
Nutt. Ornith. Club, Cambridge, Mass. Vol. VII., No. 4, Oct., 1882, pp. 213-221,
Fig. B. The same figure is also given in Coues’ Key to North American Birds, 2d
ed., p. 241.

2 SHUFELDT, R. W., “On a Collection of birds’ sterna and skulls, collected by
Dr. Thomas H. Streets, U. S. Navy.” Proc. U. S. Nat. Mus., 1887, pp. 376-387.
The lacrymal bone in the Raven C. corax sinuatus is alluded to here, but is more
fully described in a paper by the writer, which we will have occasion to quote further
on. The morphology of the lacrymal bones stands in some need of more careful
research among the Passeres, and for the class at large it is subject to a wonderful

series of variations. To instance this, we have but to compare the lacrymal in such
forms as Ortyx, Anas, and Sturnella.

86 SHUFELDT. (VoL. III.

Huxley long ago drew up for us in the most lucid terms his
excellent description of the salient characters to be found upon
the basal aspect of the skull of an average passerine bird, leav-
ing but little to be done here beyond instituting certain minor
comparisons, and further on, pointing out exceptions to his gen-
eral rule, which more recent investigations have brought to light.}
Szalia is strictly passerine in the structure of these parts, espe-
cially in the form of the vomer, as Professor Huxley describes
that bone in the work just quoted. In a specimen of Szalza.
mexicana, however, the maxillo-palatines are peculiar; their
stems being markedly slender, while their mesial free ends are
bulbous and hollow, with a full opening, in either one, to the
outer side.

In a specimen of Sza/ia arctica, a nestling, these bones have
much the same form, though the free ends are not as bulbous
at this age, and they come in contact, on either side, with the
pointed free anterior end of the inner lamina of a palatine. As
the form of the skull changes, due to advancing age, these ele-
ments recede from each other, so that in adult specimens no
such relation is ever discernible. A palatine is characterized in
having its lamina very short in the antero-posterior direction ; the
postero-external angles rounded; and the premaxillary process
long and slender, being widely separated from the fellow of the
opposite side. The rostrum of the sphenoid is rounded, thick,
and stout; while each pzerygotd is comparatively long and slen-
der ; and a guadrate wide in its transverse direction. Nothing
need be said as to the manner of articulation among the bones I
have mentioned, as in each case it is strictly passerine in Szalza,
and we have been long fully informed upon such matters.

We find nothing beyond what is already known to us in the
internal aspect of the cranial casket of a Bluebird, nor in the
sclerotals of its eyeballs, its ossicula auditus, the sesamoids
posterior to the mandibular articulations, nor in its hyoidean
apparatus.

1 Huxey, THos. H., F.R.S., etc., “On the Classification of Birds; and on the
Taxonomic Value of the modifications of certain of the Cranial Bones observable in
that class.” P. Z. S., 1867, pp. 450, 451. And to enlist a foot-note of Prof. Huxley’s,
as the works are not at my hand, the reader is also invited to refer to Nitzsch,“ Ueber
die Familie der Passerinen,” in the Zezéschrift fiir die gesammten Naturwissenschaf-
zen, 1862, and the article “ Passerinee ” in Ersch and Griiber’s Zzcyclopedie, 1840.

No. I.] NORTH AMERICAN PASSERES. 87

Feebleness of structure seems to characterize its mandzble, or
rather that bone throughout the genus; it being of the typical
V-shape pattern, with shallow ramal sides, having rounded upper
and lower margins; a conspicuous, sub-elliptical ramal vacuity
on either side ; while the bone as a whole shows a slight though
abrupt flexure downwards just beyond its middle. As for the
symphysis, it is short, convexed below, concaved above; and at
each hinder extremity the articular cup develops a posterior-pro-
jecting process, which is directed slightly upwards.

Taking aspecimen of Sza/za arctica as an example, we find that
in its vertebral column there are 19 vertebrz included between
the skull and the pelvis; of these, the first twelve are without
free ribs, —the leading minute pair of riblets occurring on the
thirteenth vertebra. On the fourteenth vertebra, the pair of
ribs, although not connecting with the sternum, are much better
developed, and may possess uncinate processes. The last five
free vertebrae of the spinal column are true “dorsals,” if we may
so nominate vertebrae which support vertebral ribs, that not only
have uncinate processes, but connect through hzmapophyses
with the sternum, as these all do. There is also a delicate pair
of sacral ribs, which usually are devoid of processes, and whose
hamapophyses fail to reach the costal borders of the sternum.
Upon examining specimens of Merula, Turdus, and Myadestes,
as well as the Varied Robin (4. x@vza), I find that they all cor-
respond in this particular with Sza/za, both as to number of ver-
tebrze, the ribs, and their epipleural appendages. Doubtless it is
the formula for all true 7uraide.

Bluebirds have rather a shallow fe/vzs, short in the antero-
posterior direction, and with the hind ends of the post-pubis
and ischium, on either side, inclined to flare outwards. The ilia
are never in contact with each other; quite the reverse, for the
groove upon each side of the sacral crista in front is wide, caus-
ing the total interval in this region to be quite considerable. In
mid-postacetabular space we always find the double row of parial

1 Since the above was written, an excellent paper has appeared from the pen of
Mr. F. A. Lucas, entitled ‘Notes on the Osteology of the Thrushes, Miminz, and
Wrens” (Proc. U. S. Nat. Mus., 1888, pp. 173-180). It not only contains much
osteological information on the groups treated, but is illustrated by a number of
useful outline figures, that may well be compared with what we have to say further
along,

88 SHUFELDT. (Vou. III.

foramina — the interdiapophysial vacuities among the uro-sacral
vertebrz. Viewed laterally, we observe that the obturator for-
amen and the circular acetabulum are of nearly the same size,
while the sub-elliptical ischiadic foramen is about five times as
big as the last-mentioned aperture. The obturator space is
closed in front, but open behind where the ischium is simply
tangent to the slender end of the post-pubis. As near as I can
tell from the pelvis of an adult Sza/za, there appear to be eleven
vertebrze fused together to form the pelvic sacrum, and they are
peculiar in having their common centra flattened upon the ven-
tral aspect, and marked by a double longitudinal row of little
squarish pits, from the first to the seventh inclusive.

The first three sacral vertebrze (dorso-sacral) throw out on
either side strong diapophysial braces which abut against the
ilia ; the two succeeding vertebrze lack these, they are aborted ;
in the sixth and seventh they are long and slender, and again
reach out to the ilia as supports opposite the acetabule. Thus
we see that these birds possess a good average passerine pelvis,
and as we proceed occasion will be taken to point out the differ-
ences existing in other types and species.

Szx free vertebrz and the terminal pygostyle constitutes the
skeleton of the tail in Sza/za, in all of the specimens I have thus
far examined.

Members of this genus possess a sternum of a typical passer-
ine pattern, and so well-known is this that it requires no special
description from me here. This pattern, I would incidentally
remark, — for we will be obliged to return to this subject again in
the present memoir, — varies but slightly throughout the entire
order of passerine birds, and is markedly uniform in its shape,
so that a true species of this enormous group can be diagnosed
almost in an instant, and to a certainty by a glance at its ster-
num. Sir Richard Owen called it the ‘“ cantorial sternum,’ ! but
this is hardly the proper appellation to apply to it, because the
pattern is almost identically the same in the clamatorial birds,
and they do not sing. (See Fig. 20 of the second Plate to the
present paper.)

In Merula, the form of the sternum departs but little from
the bone in Szalia ; the “body” perhaps being a little narrower,

1 OwEN, R., Comp. Anat. and Phys. of Verts., Vol. I1., p. 20, Fig. 15.

No. 1.] NORTH AMERICAN PASSERES. 89

and the carina a little deeper in proportion.!_ So, too, for all the
Sparrows and Finches, the fundamental form is the same
throughout,? and it is familiar to every tyro in zodlogy.

These Blue Thrushes (e.g. in S. szalia) possess a scapula in
their shoulder girdles of a very distinctive form, common to
them and most true 7urdide@. The bone is of the usual passe-
rine pattern, with its posterior fourth somewhat expanded, while
the extremity is obliquely truncated from within, outwards, and
the terminal apex, drawn out with a little point, is turned some-
what inwards towards the mesial plane.

The coracozd is comparatively a long bone with slender shaft,
the sternal moiety of which latter always develops an osseous,
wing-like expansion, that gradually increases in width from its
commencement above, downwards. The head of the coracoid
is crooked over toward the mesial plane, and is of tuberous pro-
portions as in most all Thrushes.

The os furcula is invariably of the U-shaped form, with its
lower half gracefully and gradually curved towards the keel of
the sternum; the lower midpoint supporting a conspicuous hypo-
cleidium. The free ends of the limbs of the os furcula in Stalia
are always enlarged, being laterally compressed, and when the
bone is articulated zz sztu, they, on either side, are in contact
with the head of the corresponding scapula.

Being well known in so far as its skeletal features are con-
cerned, it only becomes necessary to bear in mind the principal
points in the osteology of the pectoral limb of Sialia.

We are to observe the presence of the os humero-scapulare,
and of the small sesamoid at the elbow-joint, common to most,
if not all Passeres.

Further, it is to be noted that the bones of this limb, as well
as those of the pelvic extremity, are always non-pneumatic,
though the pneumatic fossa of the humerus is invariably capa-
cious, and to make it appear more so, the head of the bone curls
over an adjacent concavity, juxtaposed to the first-mentioned
one. At the lower or distal end of the humerus, an “ epicondy-
loid process” is ever present, while the shaft of the bone is not

1See my figure of the sternum of Merula migratoria in the second edition of
Coues’ Key to North American Birds, p. 145, Fig. 58.

2 For a Sparrow, see the figure of the sternum of one of these birds in Prof. M.
Harbison’s Elements of Zovlogy, p. 34, Fig. 9.

jeje) SHUFELDT. (VoL. III.

as long comparatively as it is known to be in other passerine
birds, and in this particular it curiously approaches the Swal-
lows.

Neither w/ma nor radius, nor the ossicles of the carpal joint,
present anything worthy of special note. The carpo-metacarpus
is characterized by a rounded laminar process projecting from
the edge of its main shaft upon the palmar aspect, at the prox-
imal third, which slightly overlaps the auxiliary shaft of the
bone, or the shaft of the middle metacarpal, which, as we know,
fuses with the carpo-metacarpus. Such a process is also present
in certain Ga//ine, where the writer has figured it.!

Two points more: the form of the proximal phalanx of the
index digit is to be noted, it being flat upon its palmar, and pro-
foundly excavated upon its anconal aspect; the remaining is,
the terminal phalanges of the digits in the Passeres do not, so
far as I am aware, ever support claws, and to this rule Szadza
forms no exception.

With respect to the skeleton of the pelvic Limb, its salient
characters are thoroughly known to the morphologist, and we
wish here to note simply the fact that in Sza/za, as in other
passerine birds, the fated/a is always present, and the fdula
always a comparatively short and filliform bone which never fuses
with the tibio-tarsus. My memoir on the osteology of Lanzus
gives figures and the usual forms assumed by all these bones of
the extremities, and they vary but very little throughout the
group.

Figures 3 and 26 of the Plates give views of the skull of Hes-
perocichla nevia, and when we come to compare that part of the
skeleton with our skull of Sza/za, we are surprised to see how
much they really are alike; indeed, the skull of the Bluebird
would nearly answer for a miniature of the skull of the Varied

Robin. It would be sinking quite to trivial details to attempt’

to enumerate the insignificant departures in one from the other.
The superior osseous mandible in Hesperocichla is straighter
than it is in Sza/za, and a swell occurs in its tomia beneath the
narial apertures (Fig. 26), and were a series of this skull reduced
to the size of an equal series of skulls of Szadza, this character
might be, if constant, sufficiently evident to enable us to make

1 SHUFELDT, R. W., Osteology of the North American Tetraonide, Plate VIL,
Fig. 58.

.

No: 1.] NORTH AMERICAN PASSERES. gI

a correct diagnosis in differentiating the two series were they
mixed up together. Perhaps, too, comparatively speaking, the
cranial capacity in such a species as Szalia mexicana is greater
than it is in Hesperocichla, and the day is not far distant when
relative size of brain is to be given its weight in determining
the position of a bird in the system. Passing to the remainder
of the axzal skeleton in Hesperocichla, we find that although it
is essentially and fundamentally the same as it is in a Bluebird,
yet in its general facies it more nearly approaches the corre-
sponding parts of the skeleton in Merula. This is quite true of
the pelvis and sternum ; but at the best the differences among
all three are but very slight,‘and a pelvis of a specimen of Szadca
arctica in my hand is practically but the pelvis of Merula m.
propinqua reduced, which I hold in the other, — character for
character, —though I believe it is possible there may be one
less vertebra in the pelvic sacrum in the Sza/za than there is in
the Robin ; but I will not positively vouch for this until I have
had the opportunity of counting them in a number of the zest-
lings of the two species.

To all intents and purposes, Werula migratoria has a skull
and associate structures like those parts in a great overgrown
Bluebird, so much are they alike. A good distinguishing feature
here, however, are the osseous tympanic bullz in the Robin, a
species wherein they are strikingly conspicuous and large. The
truth of this may best be demonstrated by taking an anterior
view of the skull of JZerula, where these bony, flaring ear-
couches strike our eye at once, while in Hesperocichla and
Szalia they would hardly attract any special notice. There
would be no difficulty in deciding between the skeletons of
Merula and Hesperocichla as to the species they belonged to, —
a glance at figures 2 and 3 will satisfy us as to the truth of this,
where I have drawn the superior aspects of the skulls of the
representatives of these two genera, and similar differences may
be detected in the remainder of their skeletons.

Turdus a. pallasit as representing its genus has a skeleton
the very counterpart of the skeleton in Hesperocichla, being in
size about one-third less.

Thus it will be seen how, osteologically, our American 7ur-
din@ are closely linked together, and they naturally form a very
well-defined sub-family of Birds, but I fail to discover anything

92 SHOFELDT. (VoL. III.

in the skeleton of any of them, so far as that part of their anat-
omy goes, which entitles them to be ranked as the highest
forms of the class.

Myadestes townsendii, of the remaining sub-family of the
Turdid@, is a species that has been made to occupy a number
of different positions in the system by various taxonomists ;
but so far as its skeleton indicates, there can be no doubt but
that it is now classified correctly by us. By a glance at figures
I and 24 of the Plates, one can be at once satisfied that the
cranial characters of this bird show it to be nothing more nor
less than a true Thrush, though the fore-part of the skull is nota-
bly wider than the skulls of the Zzrdin@,; but I would add that
the skull of an adult AZyadestes bears a curious resemblance to
the skull of a young Szalza, taken at a time when the bird is
about ready to quit the nest. For the rest, the skeleton of this
Solitaire is pre-eminently turdine, with a few peculiarities which
it may claim as its own. The keel of the sterzum is compara-
tively shallow, pointing to the fact that J/yadestes is not a bird
of strong flight, which in reality we know to be the case.
Already I have shown that in its vertebral column and ribs it
agrees with the Zurdine,; we may add that it has also szr free
caudal vertebrze and the pygostyle in the skeleton of its tail,
and this latter piece is large, and with broad posterior face.

The elvis is peculiar, or at least departs from the more typi-
cal thrushlike pattern, in that it has its obturator space and
foramen, on either side, not usually separated from each other
by an osseous division, and the hinder ends of the post-pubis
and ischium fuse with each other. In JZeru/a it must be re-
membered that in its pelvis the ischium always develops a con-
siderable bony span that completely shuts off the obturator
space from the adjacent foramen of the same name, and the
foot-like posterior end of an ischium never fuses with the post-
pubis, though they are closely fitted upon each other. The sixth,
seventh, and eighth vertebrz of the cervical division of the
spinal column in Myadestes are distinguished for the unusual
length which their pre- and post-zygapophyses attain, more espe-
cially the latter, a fact we cannot fail but notice upon the most
casual inspection of this part of the skeleton in the Solitaire.

In a recent report of mine to the American Ornithologists’
Union, entitled “On the Position of Cham@a in the System,”

No. 1.] NORTH AMERICAN PASSERES. 93

and which will appear elsewhere, I have gone over and quite
thoroughly presented accounts of the skeleton in the Families
Syluiuda@, Paride, Certhiide and Troglodytide, so it will not be
necessary to reproduce this work in the present connection;
suffice it to say that in so far as the first of these families are
concerned, the writer has not as yet had the opportunity of
investigating the osteology of Phyllopseustes borealis, but with
respect to the remaining two sub-families of this group, the
Reguline and the Polioptiline, they seem at present to be
classified in accordance with a natural system, and have been
assigned places in keeping with their structural characters as
we now understand them. In figures § and 6 of the Plates, I
have drawn superior views of the skulls of a Regulus and a
Polioptila ; and although these birds possess a skeleton in each
case essentially passerine, it in no way shows any especial
affinity with the 7wrdide@, at least any more than do the skele-
tons of a number of other representatives of this Order.
Auriparus flaviceps of the next following Family, the Paride,
I have never yet had the opportunity to examine,! but am fully
satisfied that Chamea fasciata is a Tit, that has its nearest affin-
ity in the representatives of the genus Psa/triparus, — that is, in
so far as I have examined it, and its North American congeners
are concerned, — and has, moreover, I think, certain troglodyti-
dine characters still clinging to its organization, which perchance
may have been derived from the stock from which Ga/eoscoptes
carolinensis sprang, in common with Wrens, Thrashers, and
Nuthatches, etc. This may possibly account for Chame@a and
Galeoscoptes being alike in some particulars, as the uniformity
of color of their plumage, its laxness, the scutellation of the
tarsi being nearly obsolete in each species ; somewhat similar
habits, and finally both laying wnspotted blue eggs. Of course
should such an affinity exist, it can be but very remote. The

1 At this point I desire to say that since the above was written I have received a
beautiful series of specimens of Aurzparus from my friend, Mr. Herbert Brown of
Tucson, Arizona, who has likewise, with very great generosity, sent me much other
material from his region, illustrative of the group of birds we now have under con-
sideration. This and much more will now have to be incorporated in my paper
upon Chame@a, and a supplementary paper or two which I hope to bring out upon
the morphology of the North American Passeres, some time in the future, wherein I
intend to compare more thoroughly my work with the published labors of W. K.
Parker and others in the same fields.

94 SHUFELDT. (Vou. III.

Chickadees are true Titmice, and in my opinion more highly
organized birds than the Zurdide, as they have proportion-
ately larger brains, and in many cases build nests of a high
order of architectural design; and, according to Coues, “the
young closely resemble the parents, and there are no obvious
seasonal changes of plumage.’! Sub-genus Lophophanes, in-
cluding the Crested Titmice, should be made to constitute the
genus Lophophanes, as these birds show a very distinct structure
from the Chickadees, entitling them fully to generic rank. In-
deed, in such a species as the Gray Titmouse (P. znxornatus
griseus), 1 found, among other distinctive characters, that it had
a vomer of an oblanceolate form, being fozzted in front. This
extraordinary fact even constitutes a marked departure from the
type that bone assumes among the Passeres generally. Huxley
laid it down as a law that in the A®githognathous birds “the
vomer is a broad bone, abruptly truncated in front, and deeply
cleft behind, embracing the rostrum of the sphenoid between its
forks.” 2 Figures 7, 8,9, and 10 of the Plates to the present
memoir, give superior views of the skulls in Crested Tits, Tits,
Chamea, and the Bush Titmice.

Nuthatches (see Fig. 11), as the remaining Family of the Par-
id@, are possessed of a passerine type of skeleton characterized
by anumber of features peculiarly its own. Szt¢a c. aculeata, for
instance, has the vomer very small, though of the usual passerine
form; its Jacrymal bones remain free throughout life, occupy-
ing, on either side, a position in front of the pars plana, as in
certain Corvide,; the interorbital septum is commonly entire,
and rather dense; specimens may be met with (I have one before
me) wherein the ilia meet at a point over the sacral crista, as
in Chamea, and the hinder ends of the ischia are drawn out into
unusually slender processes; finally, specimens of this Nuthatch
occur in which the “notches” of the sternum are strikingly small.
Osteologically, I should say that such a sittatine form as we
have here, is not very closely affined to the genus Lophophanes,
and we may be assured that good, strong sub-family lines define
their kinship.

Passing to the next family, the Certhzid@, I find I have said
in my Chamea essay all that I have to in reference to these

1 Cougs, E., Key to North American Birds, 2d ed., p. 263. 2 Tbid., p. 450.

No. I.] NORTH AMERICAN PASSERES. 95

Creepers ; they undoubtedly are entitled to family rank, but I
would prefer to devote further research to more extensive
material before advancing final opinions upon their definite
affinities. In my Chamea paper I give a lateral view of the
skull of C. fi americana, a species which perhaps has a trace of
the Wren in it.

In the same paper I presented the skeletal characters of a
number of Wrens and their allies (Family TZvoglodytide, see
Fig. 12), and so will have little or nothing to add about them
here. I have examined and carefully compared skeletons of
Mimus, Oroscoptes, Harporhynchus, and a number of the true
Troglodytine, and am satisfied that the Mzmzn@ are aberrant
thrushes, linked with the true 7urdid@ and the Wrens, through
such a genus perhaps as Campylorhynchus, though Ovoscoptes
has a skeleton that would pass without any difficulty whatever
for that of a true turdine type. In my paper on Czuclus in the
Nuttall Bulletin, quoted above, I gave an upper view of the
skull of this bird, and one may easily see that I am justified in
making this remark. J7Zzmus has a skeleton quite like Ovoscoptes,
and fully as Thrush-like. In Harporhnychus a decided departure
is met with, and the skeletons in some of those species are like
skeletons of great overgrown Wrens. They have a peculiar
pattern of pelvis, however, essentially their own, which is due
to a sharpness of its principal borders and angles, and a certain
amount of prominence to its most salient processes.

Still adhering to the plan adopted in the A. O. U. Check-
List, the next family we come to is the Czzc/zd@, containing the
single species Czuclus mexicanus, our American Dipper, and of
it I said in my paper on its osteology (Bull. Nutt. Ornith. Club,
1882), that it is quite closely related to the genus Sczuvus, and
not far removed from some of the Wrens; while Coues has re-
marked that this is a “small but remarkable group, in which the
characters shared by the 7urding, Saxicoline, and Sylviine, are
modified in adaptation to the singular aquatic life the species
lead.” (Key, 2d ed., p. 255.) Now, I have all my old material
before me upon which my conclusions were based as given
above, and a great deal more besides. I can see in C7uclus
where I saw the Wren in its skeleton, for in its skull there is
that evident resemblance to the turdo-troglodytine stock, while
other points clearly show its affinity with the Water Thrushes

96 SHUFELDT. [Vot. III.

(Scturus); and yet, while there is much to base such an opinion
upon, the fact still remains that the typical passerine skeleton of
Cinclus mexicanus is powerfully impressed with strong turdine
characters.

My knowledge of the osteology of our American Family Mo-
tacillide rests upon my having carefully studied the skeletons
of a number of species of the genus Axzhus, and such material
is before me at the present writing.

The sku// in such a form as Anthus pensilvanicus 1s an exceed-
ingly delicate structure in all its parts (Fig. 13), the interorbital
septum being markedly deficient in bone; the pterygoids and
the zygomz wonderfully slender rods; while the palatines and
premaxillary are about as frail as we ever see them in the Class.
Taken as a whole, the skull of this Pipit is almost identically
like the skull of Sczurus motacilla, while in the rest of its skel-
eton, more particularly in the sternum and pelvis, we see some
rather strong traces of the Thrush: especially is this true of the
last-named bone; not in any ways enough, however, to detract
from the fact that the J/o¢aci/lide see their nearest affinity in
the genus Sczurus of the Minotcltzd@, and the relationship here
is very close.

This last-mentioned family is the next one we have in order
to consider, and in our American avifauna it is made to contain
the Wood-Warblers, a lovely group of birds, that in their struc-
ture seem to have a tincture of every morphological variation to
be found in the entire passerine order. On p. 287 of the second
edition of his Key, Coues says of them that “the warblers
grade so perfectly towards the tanagers that they have all been
made a sub-family Zanagride (where possibly they belong).
The affinity of some of them with Cwredzda, or honey creepers
of the tropics, is so close that the dividing line has not been
drawn.” We well know how J/cterta branches off in another
direction, while the Redstarts are strongly inclined towards the
Tyrannide. True as all this undoubtedly is, we can neverthe-
less, through a critical examination of a series of skeletons of
the genera making up the Family in this country, throw a little
light into so closely affined a group, and perhaps reveal some
of the veins of the mystery. To do this we should choose a
type-centre as it were, and this can be very well represented by
the genus Dendroica, the species of which probably presents in

No. 1.] NORTH AMERICAN PASSERES. 97

its skeleton the characters of our true warblers. Take, for in-
stance, such a well-known skeleton as that of Dendrotca coro-
nata ; it possesses all the typical passerine characters on a small
scale, and almost with a provoking likeness to some of the larger
forms of the Order. Indeed, could we bring the skeleton of
such a Warbler up in size so as to equal the skeleton of Hes-
perocichla nevia, the similitude between them would be marvel-
lously close. As one might easily imagine, the osteological dif-
ferences between D. coronata and such another Warbler as Pro/o-
notaria citrea are very slight, and the reader has but to compare
figures 3 and 15 of the Plates to appreciate the statement I have
just made. More than this, I will warrant that from a complete
collection of the skeletons of all our American Passeres, I can
choose representatives from a variety of the families that will
intergrade, both as regards size and characters, and connect such
forms as our D. coronata and H. neévia, most perfectly, and I
have just said how much the extremes of such a series are alike.
Be this as it may, let us return again to the centre of our
Warbler system, and speaking quite strictly from osteological
premises, we find from D. coronata through the genus Sczurus
the affinity with the /Zotacz/lide is easily demonstrated; no
doubt, somewhere in this kinship the Ground Warblers of
the genus Geothlypis come in. My ideas about the position of
Icterta, I have already given in my Chame@a paper, and I here
present a view of the superior aspect of its skull (Fig. 14).!
Coming back again to the skeleton of our Warbler, how easy is
the transition to the Creepers through such a creeping species
as Minotilta varia, a complete skeleton of which form is before
me. The linking with the tanagrine forms I have elsewhere
alluded to, and through the genus Setophaga perhaps, the clama-
torial group may be linked, and Vzreo possibly has a kinship
here.

Although I have never seen a specimen of the skeleton of the
Bahama Honey Creeper (C. dahkamensis), the sole representative
of the next family, the Ceredzda, still I think it is very probable
that it should stand precisely where it has been placed in the

1Just here I would invite the reader’s attention to the protuberance at the pos-
terior extremity of either zygoma in figure 14; they are the anterior ends of the
squamosal processes, and not the quadrates, as is the case in figure 1, while in figure
18 a portion of both show.

98 SHUFELDT. [ VoL. III.

A. O.U. Check-List; that is, following the Wood Warblers,
and at the end of the series which terminates with the Creep-
ing Warblers (JZ. varia). But as I say, this opinion is based
solely upon what I have read from other authors upon the topo-
graphical anatomy of these birds, and the fact that a similar
structure of tongue is common to both Creepers and some of the
Minotitide.

Arriving next at the Family Vzveonzde, we at once enter upon
an exceedingly interesting field of research, for the position of
the Vireos, for which this family was created to contain, has
always been more or less of a mooted question.

Formerly the Vireos were united with the Shrikes (Laniide),
simply from the fact that the bills of certain of the Viveonide
resembled a Butcherbird’s, and such names as Viveolantus and
Lanivireo were bestowed upon the subdivisions of the family.

The family Lanwzd@ has now been made to stand next below
the Vireos, and here it will be more convenient to deal with these
two families together, the more especially as I have already pub-
lished something in reference to the Shrikes.1 Now if we
choose for comparison the skeleton of such a form as ZL. 2. excu-
bitorides, and V. ludovictanus from among the Vireos, we see at
once that both of these species possess a skeleton exclusive of
the skull, that is essentially passerine in all particulars, but with
respect to the skull, the most striking differences at once become
evident to us, and further show most conclusively the danger of
attaching too much weight to a notch in the integumental sheath
of the superior osseous mandible, and basing affinities upon it.

Vireo noveboracensis (Fig. 16) has a skull which, to all intents
and purposes, is but slightly removed from the skull in some of
the MWinotiltide. Examining the structures at the base, and

‘critically comparing them one after the other from apex of pre-
maxillary to foramen magnum with the corresponding ones in a
skull of Protonotaria citrea, we find them to agree almost exactly.
Indeed, there appears to be but one noticeable difference ; for in
the Prothonotary Warbler the posterior external angles of the
palatines are pointed, while in the V7reo the hinder ends of these
bones aie obliquely truncated from without inwards, and even in

1 SHUFELDT, R. W., “ Osteology of Lanius ludovicianus excubitorides.” Az//.
U.S. Geol. and Geog. Surv. of the Terr. Dept. of the Interior, Vol. VI., No. 2.
Washington, Sept. 19, 1881. (Hayden’s 12th Annual.)

No. 1.] NORTH AMERICAN PASSERES. 99

this latter character it does not agree with the Shrike. Turning
to Lanzus, we meet with a skull wherein all the anterior part of
the rhinal chamber is more or less completely filled in with osse-
ous tissue of the cancellous variety; and this so far fills up each
external narial opening that there is left on the side of the supe-
rior mandible only two small apertures, an anterior subelliptical
one, and a posterior vertico-elongated one, just in front of the
nasal bone. Where this filling appears externally, it is covered
over by a layer of compact bone which is continuous with the
outer superficies of the premaxillary and nasals. (See Figs. 100
and 104 of my memoir on the Osteology of Lanzus.)

The vomer is strictly passerine in this Shrike, but the maxz//o-
palatines are comparatively broad processes and entirely lack the
mesial bulbous free extremities, present in Vzveo and nearly all
passerine birds.

Lantus has the zuner posterior angles of its palatines drawn
out into conspicuous spine-like processes, and the anterior limb
of either of these bones is broad and flat, especially where each
merges into the premaxillary.

In all old specimens of these Shrikes that I have ever exam-
ined, the palatine ends of the pzerygords fuse completely each
one with a palatine on its own side, —a very unusual condition,}
and one never found to obtain in Vireo.

Finally, the interorbital septum is far more complete as a rule
in Skrikes than it ever is in the Vireos, in which latter it agrees
precisely with the Warblers.

The mandible of Lantus is far more powerfully constructed
than we find it to be among the vast majority of Passeres, a con-
dition we would very naturally look to be the case.

Speaking strictly from osteological premises, I am of the opin-
ion that Zazzus is far more closely affined with the Clamatorial
birds than it is with Vzveo ; by this I mean that the Vireos are
well within the passerine circle, while Lanzus, also wzthin the
passerine circle, is close up to its limiting arc, while immediately
over this bounding periphery we find the Clamatores, with all
their allies, so many of which in other parts of the world possess
strong passerine characters in their economy. Compare, for

1 So firm is this fusion in some skulls that I once macerated a specimen for over
six weeks, and yet the pterygoids still remained firmly attached to the palatines, even
all sutural traces having completely disappeared.

100 SHUFELDT. [Vot. III.

instance, the skull of a specimen of /yzarchus crinitus with the
skull of Lanius 1. excubitorides, and my speculations will at once
be appreciated. See how the anterior portion of the rhinal
chamber in each is filled in with bone in precisely the same man-
ner ; the maxillo-palatines are of the same pattern, as is also the
vomer in each, and a number of minor points also corresponding.

Dentirostral bills, like zygodactyle feet and unnotched sterna,
are not always sure indications of affinity, as one and all of them
may be instances of physiological adaptation, and not indices of
fundamental morphological structure determining near kinship.
When we come better to know, —and, alas, how deficient our
knowledge in such matters yet is, — the anatomy of more of the
foreign allies of our Tyrant Flycatchers, and diverging affines
of the Shrikes, I am sure the opinion here advanced will not
be considered so wide of the mark. Such affinity as the Lan-
tide may have with the Corvzdg, I am not at present prepared
to enter upon, as the opportunity to fully examine the material
requisite for the decision of such a question has never as yet
been offered me.

Last January (1888) Prof. W. Kitchen Parker, F.R.S., kindly
defended for me, before the Linnzan Society of London, a
paper of mine upon the Morphology of the Macrochires and
allied groups of birds. In that paper is given quite an exhaust-
ive account of the skeleton of Ampelis cedrorum as a represen-
tative of the Family Ampelide ; further, both in text and plates,
the family Azrundinide is very thoroughly dealt with, the
structure of every American species being described and com-
pared. Possibly this paper will appear in the course of the
year, and in any event it obviates the necessity of my reviewing
the morphology of those forms here again. The Swallows con-
stitute a very well-defined family of passerine birds, seeing their
nearest allies in the Cyfse/z (Swifts) outside their order ; while
these latter are in no ways especially affined with the Humming
birds (Zvochilz).

I find also that I will have appear in Te Auk for October
(1888) a paper (illustrated) upon the skeleton of Habza melano-
cephala, wherein the osteology of all our principal species of the
Family /ringillide is carefully presented, so this large and
important group will not be touched upon in this paper.

Coming next to the three families of the Corvide, Sturnide,

Novi, | NORTH AMERICAN PASSERES. IOI

and J/ctertde@, it will be remembered by those familiar with the
writer’s memoirs, that they were all treated in a contribution
to the Journal of Anatomy not long ago,! and their affinities
pointed out in detail.

Finally, we arrive at the Family A/audide, the first one pre-
sented at the commencement of the sub-order Oscines in the
A. O. U. Check-List, containing as it does the Larks. Here we
have two genera, A/auda for the single species A. arvenis, the
skeleton of which I have not before me; and Ofocoris, with
eight species. A number of years ago I published a very full
account of the skeleton of Evemophila alpestris, in these days
more properly described as Ofocorts alpestris arentcola, and
having thus given a complete description of all the details of
structure in the osseous system of that species, it will be
unnecessary to essay further in that direction.? It is very diffi-
cult to tell where to place Ofocoris ; I have carefully compared
its skull with such genera as Anthus, Molothrus, Zonotrichia,
and a variety of others of the Aringillide, with Turdide and
Tits, and a host of Passeres,; but passerine as it is itself, it
presents cranial characters which seem to be peculiar to its
genus. Not the least curious of these is the fusing together,
in the adult, of the ends of the sphenotic and squamosal pro-
cesses, leaving only an elliptical foramen between them, and the
latter process being very broad in the transverse direction.
Some Gadling show this feature in their skulls —a fact which we
mention in order to explain what is meant. Newton has said,
“There is, however, abundant evidence of the susceptibility of the
Alaudine structure to modification from external circumstances
—in other words, of its plasticity; and perhaps no homogene-
ous group of Passeres could be found which better displays the
working of ‘natural selection.’’’ And again, in the same place,
“Almost every character that among passerine birds is counted
most sure is in the Larks found subject to modification. The
form of the bill varies in an extraordinary degree”’ ; from which

1 SHUFELDT, R. W., “On the skeleton in the genus Sturnella, with osteological
notes upon other North American /cferide, and the Corvide.” Four. of Anat. and
Phys., Vol. XXII. (n.s. Vol. II.), pp. 309-350. London, April, 1888. Plates XIV.,
XV.

2 SHUFELDT, R. W., ‘‘ Osteology of Eremophila alpestris.” Bull. U. S. Geol.

and Geog. Surv. of the Terr. Dept. of the Interior. Vol. VI., No. 1. Washington,
D.C., Feb. 11, 1881.

102 SHUFELDT. [Vou. III.

point this distinguished ornithologist and anatomist cites numer-
ous species of Larks with bills in some as slender as a War-
bler’s, to such a species as Rhamphocorys, where ‘it is exagger-
ated to an extent that surpasses almost any Fringilline form.” !

I am inclined to think that we have no birds in our avifauna
to which Ofocoris is especially closely related, and that as a
species it has arisen from some Old World stock, and only sec-
ondarily spread to this continent at a comparatively recent
epoch. As will be observed from the figures in my memoirs,
quoted above, the structures at the base of the skull in Ofocoris
are strictly passerine in their arrangement; quite similar, for
instance, as we find them in Azzhus, but by no means so deli-
cately constructed; rather the reverse, we should say.

In figures 22, 23, and 25 of the Plates to the present memoir
I present views of the superior aspects of the skull from speci-
mens of Habia melanocephala, Cyanocephalus cyanocephalus, and
Piranga ludovicianus, respectively ; these drawings were made
by me and here offered to the end that they might be compared
with similar views of the skulls of other passerine birds, which
have likewise been presented in the Plates, but described more
in detail in the text; the three foregoing species mentioned
belonging to forms which I have described in papers in the
hands of my publishers, but not yet in print, and in other
memoirs. Especial attention is invited to the form and marked
capacity of the brain case in the Pifion Jay (Fig. 23), one of the
Corvide, as compared with similar parts in such forms as the
Tyrant Flycatchers (Figs. 18 and 19), or even such strictly pas-
serine types as some of the Thrushes and Warblers (Figs. 4 and
5). Then again, compare this feature in such a true Thrush as
Myadestes with a Titmouse, as shown in figures I and 9 respect-
ively. Further on in my final recapitulation it will be my aim to
attempt to point out if possible the probable significance of such
an evident character as this, and in the foregoing paragraphs
I have already strongly hinted as to what my interpretation
of it may be. That it is incontestable evidence of a perfection
of organization in any vertebrate form, all the truths of paleon-
tology, physiology, and recent investigations in morphology, go
to sustain.

But we will have nothing more to do with the osteology of the

1 NewTon, A., Encyc. Brit., Art. “ Lark.” Vol. XIV., p. 316 (9th ed.).

No. I.] NORTH AMERICAN PASSERES. 103

Oscines in this place, deferring all such questions to the closing
arguments of this paper, in the “Conclusions,” where they
more properly belong, and now at once proceed to the consid-
eration of the skeleton in our American clamatorial birds, of
which there are some thirty-six species and sub-species in our
United States avifauna.

By referring to the scheme of the families as given at the
commencement of this paper, it will be seen that the clamatorial
family, the Zyrannide@, about to be considered, occupies the first
position in the list, which there means that it is of the lower,
indeed lowest, group of passerine birds, so far as we are enabled
to judge from their structure.

Coues in characterizing this family has said that it is peculiar
to America, and is “one of the most extensive and character-
istic groups of its grade in the New World, the Zanagride and
Trochilide alone approaching it in these respects. There are
over 400 current species, distributed among about 100 genera
and sub-genera. As well as I can judge at present, at least
two-thirds of the species are valid, or very strongly marked
geographical races, the remainder being about equally divided
between slight varieties and mere synonyms. Only a small frag-
ment of the family is represented within our limits, giving but
a vague idea of the numerous and singularly diversified forms
abounding in tropical America. Some of these grade so closely
toward other families, that a strict definition of the 7yraunide
becomes extremely difficult; and I am not prepared to offer
a satisfactory diagnosis of the whole group” (Key, 2d ed., p.
428). For the manner in which the family has been classified
by our avian systematists, the reader is once more referred to
the A. O. U. Check-List. The material at present at my hand,
some of which I am greatly indebted to Mr. H. K. Coale of
Chicago for, by which I hope to pass in review the skeletology
of the Zyrannide, comes mainly from the genera Tyrannus,
Mytarchus, Sayortus (all three species), Coxtopus, and Empidonax.
Figures 18 to 21 inclusive, of the Plates, illustrate skulls and
other bones of these birds; and when speaking above of the
craniology of Lanzus, I dwelt to some extent upon certain
features which characterize the skull of Myzarchus. As a rule
in these Zyrannide, the brain-case is comparatively small and
the sides and vault of the cranium rounded. Relatively, the

104 SHOPELDT. [VoL. lil.

brain-case seems to be larger in such a species as 7. tyranniis
than it is in some of the other genera. This feature in them
all, however, is made to be still more apparent by their great,
wide, and flat superior osseous mandibles, which constitute such
a striking character in the skulls of the vast majority of these
Tyrant Flycatchers. When we come to examine the bony, upper
beak, in such a form, for instance, as the King-bird (7. tyrannus),
we find that the external narial apertures are large and sub-
elliptical in outline, and these, when covered by the thinner
posterior part of the horny sheath of the mandible, constitute
the nasal fossz of descriptive ornithologists. It is in the ex-
treme fore part of either of these that the small subcircular and
functional nostril opens, while in some species, or certain indi-
viduals of some species, nearly all this anterior part of the
rhinal chamber may fill in with bone, in a manner I have already
described above. A slit, on either side, just in front of the nasal
bone, remains open (but is always covered with the integumental
mandibular sheath), and the aforesaid aperture comes to be the
true outer nostril. In figure 19 I show this condition in a
specimen of JZ. crinztus, but in another skull before me of JZ.
cinerascens, very little bone is deposited in these parts, they
being more like the skull of the Black Phoebe shown in figure
18. All grades of this condition are to be met with between
these two extremes. Sometimes a small, curled piece of bone
remains free, on either side, within the rhinal chamber, and, held
in place by surrounding structures, resembles a “turbinal bone”’ ;
and in addition to these, the /acrymat/s remain free in these clama-
torial birds, being situated, in each case, immediately anterior to
the pars plana. These I have figured for MZ. crinitus in my
paper on the Macrochires, in the hands of the Linnzean Society
of London.

Flat, and for the most part smooth, the under side of the pre-
maxillary region of the skull in front is bridged across with a
thin, bony layer, a condition rarely found among our oscine pas-
serine birds, except in such species as Setophaga.

Tyrant Flycatchers, as a rule, have the interorbital septum
far more perfectly completed in bone than do either the Warblers
or Thrushes, or the nearest allies of these latter; and in JZ. czne-
vascens a large foramen exists between the mesethmoid and
the pars plana, immediately beneath the frontal region of the

No. I.] NORTH AMERICAN PASSERES. 105

skull. The vomer is fashioned much as we find it among the
average oscines, but the maxillo-palatines always depart in their
pattern from those birds, for they are broad where they come
away from the maxillaries, and gradually taper to their free
mesial ends, which are never finished off by a bulbous extremity,
such as we find in Harporhynchus, for instance, though I have
found in JZyarchus the points of the maxzllo-palatines bent
backwards, thus simulating the condition referred to in the more
highly organized Passeres. We usually find, too, a foraminal
opening piercing the base of either maxzllo-palatine in the
Clamatores, a feature especially conspicuous among the larger
American species, though commonly present in a more or less
marked degree in them all.

The interior of the cranial casket seems to offer us no very
good characters which can be utilized, either in classification, or
in any way, beyond the question of relative capacity, point to
the affinities of the several groups under consideration.

These Tyrant birds always seem to have the sclerotal plates
of the eyeballs very narrow, and in old specimens these show an
evident tendency to fuse together, and ina specimen of Sayornis
nigricans at my hand this has actually taken place. Nothing pe-
culiar characterizes either the hyoidean apparatus or the ossicles
of the ears. The mandible is not much stronger, in comparison
with the size of the various species, than we find it among birds
of an equal size in the oscine group; and in Lanzus it is much
the stronger. J/yzarchus ctnerascens, for example, has the sym-
physis to its mandible wide, shallow, and yet rather deep in the
antero-posterior diameter; the rami are narrow in the vertical
direction, the vacuities small, and the articular cups and pro-
cesses respectively shallow and feebly developed.

It will be seen from this brief description that very excellent
differential characters distinguish the skulls of typical oscine
and clamatorial birds. Not so, however, with the remainder of
the axial skeleton, nor with the appendicular skeleton ; for in all
the Zyrannide examined by me I find the vertebral column and
ribs arranged upon the same plan as in the vast majority of the
oscines, with shoulder girdle, sternum, and pelvis of the same
general pattern. One thing must be nevertheless noted, and
that is, that the skeleton is far more pneumatic among the
Clamatores than it is usually found to be in the Oscines, —

106 SHOUFELDT. (VoL. III.

the humerus (and sometimes the femur?) is always pneumatic,
and in Myzarchus a single row of quite sizable foramina extend
the entire length of the middle line of the sternum adown its
thoracic aspect. I am inclined to think, too, that other long
bones in the skeleton of this species have the air admitted to
the cavity of their shafts; but here I judge only from appear-
ances ; for if the foramina be present, I failed to find them, even
with the aid of a good lens, in some cases.

With this succinct account of the osteology of some of the
genera of our American 7yrannide, I will close the general de-
scriptive part of my memoir, and pass to my conclusions, based,
as these latter will be, upon the facts herein brought out. In
this place, however, I would like to add that Iam aware that I
have not touched upon the embryology of any of the species
treated, nor was that my aim originally. The paper proposes
nothing further than a general description of the skeleton in
adult forms, and such deductions as we may logically make
upon the comparison of such data. No doubt when we come to
critically consider the embryology of many of the species, and
draw more elaborate comparisons, a great deal of additional in-
formation will be gotten at, and some of the more complex
questions in affinities by such means be decided. Especially
will this be true in the case of comparing the embryos of Zyvan-
nide with those of the Lande and Setophaga and others.

The most I can hope for the present effort, is to establish
broad lines in the osteology of the Passeres of this country, and
present a framework, as it were, which may serve as a basis
upon which may be reared in the future those refinements in
avian morphology, that forever tend to shed a more certain light
upon all vexed questions in the taxonomy of this perplexing Class.

CONCLUSIONS.

For fully ten years past and more, the writer has busied him-
self with the anatomy of the passerine birds of this country,
during which time he has also read many of the works of others
upon the same subject; so then, although this memoir deals
alone with the osteology of the order Passeres, it is very likely
that now we come to sum up our knowledge in these fields, and
draw our conclusions, and offer our opinions as to classification
and affinities, —it is very likely, I say, that we will not be en-

No. 1.] NORTH AMERICAN PASSERES. 107

tirely governed in such matters by osteology alone, but will be
more or less influenced by other considerations, such as our
knowledge of the habits, range, nidification, anatomy of the
various systems, plumage of young, and general morphology of
the species dealt with.

At the commencement of the present paper, I gave a list of
the passerine families arranged in the order given in the A. O. U.
Check-List, starting in with the 7yrannzde, and ending with the
Turdide, the first supposing to represent the least specialized
types in their organized structure, and the last the highest.
Now I will here give a scheme of the same families, rearranged
in accordance with the facts sent forth above, and other data
in our possession, and follow this rearrangement by a few words
in its defence.

ORDER, SUB-ORDERS, FAMILIES.

¢Clamatores . Tyrannide.
Laniide.
Ampelide.
Hirundinide.
. Alaudide.
Certhiide.

. Vireonide.

. Motacillide.
. Sylviide.

Io. Coerebide.
11. Mniotiltidae.
12. Cinclide.

13. Troglodytide.
14. Turdide

15. Paride.

16. Tanagride.
17. Fringillide.
18. Icteridz.

Ig. Sturnide.
20. Corvide.

ON AM BW DN

Ne)

PASSERES 7) Oscines .

Professor Alfred Newton, F.R.S., has advanced very cogent
reasons for placing the Corvide at the head of the Passeres,
already cited above, and the present writer fully coincides in his
opinion, and further believes with that eminent authority, that
the Raven should lead the family. Corvus corax has a skeleton
of the highest type of oscine organization, a statement that

108 SHUFELDT. [VOL. III.

applies with equal force to much else in its economy ; its brain
is relatively larger, in proportion to the size of the bird, than
others of the order; its young substantially have the plumage
of the parents at atime when as nestlings they first take on
their plumage ; and finally, the Raven is a far more intelligent
bird than any species of Sza/za that the author has ever made a
psychological study of, and, indeed, than any other Thrush. The
power of song is by no means an index of a high order of intel-
ligence, much less an indication of a highly specialized organiza-
tion.

Through their natural structural affinities, the Corvide must
next be followed by the Sturnid@ and /cterid@, and through such
linking species as Molothrus and Dolichonyx these must be fol-
lowed by the Fringz//id@, whereas no family can stand between
these latter and the Zanagrid@. Admitting then that the Cor
vid@ are fully entitled to stand at the head of the Order Pas-
seres, and that the Starlings, Orioles, Finches, and Tanagers
follow as a natural series or sequence, I am fully convinced
that the Parzdeé should, by all our previous arguments, enjoy the
next position of distinction. Indeed, were it not totally out of
the question to introduce a family zz among the first five I have
placed first in the list, the Pavzde might hold a more exalted
rank, for in my opinion the group of Tits and their more imme-
diate affines are birds of markedly high organization. They
possess unusually large brains for their size; there is just a pos-
sibility that they are connected with the Corvzde through such
a species as Perisoreus ; they show wonderful ingenuity in the
construction of their nests; the plumage of the young is almost
identical with the parents; and finally, some of their kin (as
Chamea) have absolute scutellate podothece.

As to this last character, referring as I do to the “ booted”
tarsus, or a tarsus which shows in the adult a continuous podo-
thecal envelop, granting that it is an indication of high special-
ization of structure in birds, I am in no way prepared to say
that it is to be outweighed by a relatively larger brain for any
particular species. The size of the brain in my judgment, as
compared with the size of its owner, being by far the better
criterion of perfection in general specialized structure. Perhaps
the “booted tarsus,” and such a degree of refinement in structure
as we find in the turdine syrinx, may be claimed to be on a par.

No: Tr: | NORTH AMERICAN PASSERES. 109

There is another character of no inconsiderable importance,
and may perhaps be entitled to greater weight than the booted
tarsus, and that is the reduction of the tex primaries of the wing
to zine. The Tanagers show this feature, and it is a good one
to hold them in the place which I have assigned them; more-
over, it gives them precedence over the more lowly organized
Turdid@, which in reality should long ago have been recognized.

Few, however, will question the claim of the 7urdid@ to the
next place in the series, and it is there that they have been
placed in my scheme. High organization in them is seen in
some of the species having relatively rather large brains; in
the booted tarsi of some of the species; in the syrinx; in the
Turdin@é possessing a spurious first quill; and some few other
minor points. Evidences of their being structurally and psycho-
logically lower in the scale are seen in their young having a first
plumage which in all cases is different from the plumage of the
adult ; in some of their near affines having comparatively small
brains; in none of them showing a marked degree of intelli-
gence; finally, in some of their near kin being aberrant forms
of rather a low order of organization, as Orvoscoptes.

Structurally linked with the Zuvdide, we have the Troglody-
tide, their nearest affines in our avifauna, and I have ranked
them next in my series. Following these I have placed the
Cinclide, as Cinclus undoubtedly has strong turdine affinities,
and perhaps some kinship with the Wrens.

Below the Czxclide I have placed our family of Wood War-
blers (Zinotz/tzd@), containing as it does such thrush-like forms
as are found in the genus Sczuvus, which, osteologically at least,
appear to be related to Czmclus. In this group Setophaga de-
mands a far more careful examination than it thus far has ever
received, and I believe it was McGillivray who threw a shade of
suspicion over its morphology by saying that its syrinx was very
much the same as we find it in the Clamatores. At present I
have only an imperfect skull of a Redstart before me (5.
ruticilla), and have met with none of this genus for several years
past. From such a genus as MJznotilta of the MWznotilttde, we
' pass naturally to the Cwrebzde, and I have allowed them to stand
next in my series. These latter are followed next below by the
Sylviide, containing such forms as the Kinglets and Gnat-
catchers, birds that, although in the former the tarsus is booted,

IIO SHUFELDT. [VoL. III.

and the first quill of the wing spurious, are birds of relatively
very small brains, and the young males in Regulus calendula, at
least, do not take on the plumage of maturity until the second
year. Good, strong, sub-family lines must be recognized as
being drawn between the Reguline and the Polioptilina.

From the last three-mentioned families in my serial arrange-
ment, we pass naturally to such groups as the Motacillide
and Vireonide,; the former being hardly anything more than
terrestrial Sylvias, and the latter, judging from their skeletons,
have closer affinities with the Warblers than with any other
family which we have thus far investigated. After these the
true Creepers (Certhizde) have been placed, forms which, oste-
ologically and otherwise, have no especial claim to be ranked
with birds of undoubtedly higher organization. This remark
applies with equal force to the Alaudide,; indeed, still more
pointedly to them, for the Larks in addition have an anomalous
structure of the tarsal theca, and one from its double scutella-
tion of perhaps a lower type organization. In them, too, the
young have a different plumage from the parents.

For a long time I was at a loss to know where to place the
Swallows ({/zrundinide), and they have been crowded to near
the foot of the list, not that they have not a few points in their
economy indicative of a certain degree of rather high specializa-
tion ; still, although truly passerine birds, they are birds of com-
paratively small brains, and their young differ in their plumages
from the parents; and, while we do not yet know the exact
affinities of the Wzrundinide, all the speculations in that quarter
have been in the direction of associating them with groups of
recognized low type of organization.

Newton says of them: ‘ But altogether the family forms one
of the most circumscribed, and therefore one of the most
natural groups of Osczues, having no near allies; for, although in
outward appearance and in some habits the Swallows bear a
considerable resemblance to Swifts, the latter belong to a very
different order, and are not passerine birds at all, as their struc-
ture, both internal and external, proves. It has been sometimes
stated that the Hzrundinide have their nearest relations in the
Flycatchers; but the assertion is very questionable, and the
supposition that they are allied to the Ampelide, though possibly
better founded, has not as yet been confirmed by any anatomical

No. 1.] NORTH AMERICAN PASSERES. III

investigation. An affinity to the Indian and Australian Artamus
(the species of which genus are often known as Wood-Swallows,
or Swallow-Shrikes), has also been suggested ; and it may turn
out that this genus, with its neighbors, may be the direct and
less modified descendants of a generalized type, whence the
Firundinide have diverged ; but at present it would seem as if
the suggestion originated only in the similarity of certain habits,
such as swift flight and the capacity of uninterruptedly taking
and swallowing insect-food on the wing.” (A.N., Brit. Encyc.,
oth ed., Vol. XXIT., p. 730.)

Huxley has said “the Cypselide are very closely related to
the Swallows among the Coracomorphe” (P. Z. S., 1867, p.
469); which is equivalent to my having substantially said, in
another connection, that the Cypse/z are but profoundly modified
Swallows, which latter are their nearest affines among the Pas-
serves. So taking it all and all, I am at present inclined to be-
lieve that the Swallows represent rather a low type of organiza-
tion among the passerine birds.

The Ampelide, which I have placed even lower in the scale
than the Azrundinide, show in their organization all, or nearly
all, those features which, as we now interpret them, are indica-
tions of an inferior grade of avian organization. All of these
characteristics I have elsewhere fully dwelt upon and pointed
out in detail.

In the body of the present memoir, the writer entered quite
largely upon the question, as to the reasons for assigning the
Lanide a \ow place in the passerine order, and it will be unnec-
essary to take up that part of our subject here again. I am of
the opinion that they are as low, if‘not the lowest type of bird-
structure we have in our United States avifauna, among the
Oscines.

The classification of our sub-order of clamatorial birds, as rep-
resented by the 7yrvannide, requires no especial comment from
me, in this place; it has been left in the same position it occu-
pies in the A. O. U. Check-List, and probably meets with the
views of the majority of ornithotomists, as well as the systemat-
ists the world over. It seems, I think, fully supported by all
that we at present know of their economy.

112 SHUFELDT.

Note. — With the exception of figures 24 and 26, all the drawings in the Plates are
of the size of life; the excepted figures being twice the natural size. They were all
drawn by the author directly from specimens in his own cabinet, with the exception
of the skull of Sita c. aculeata, which belongs to my son (Fig. 16). The skeleton
of Ampelis cedrorum was presented me by Mr. H. K. Coale of Chicago, and the
Sayornis nigricans by C. A. Allen of Nicasio, California; while the Smithsonian In-
stitution generously furnished the specimen of the Varied Thrush (4. xevia), shown
in figures 3 and 26. All the others, with a few exceptions, were collected by the
author in various parts of the United States, as Wyoming, New Mexico, Louisiana,
and elsewhere.

EXPLANATION OF PLATE V.

Fic. 1. Superior view of the skull of AZyadestes townsendii; ad. , New Mexico.

Fic. 2. Superior view of theskull of A/erula migratoria propingua, ad. ¢.

Fic. 3. Superior view of the skull of Aesperocichla nevia, ad. g. (No. 81,166.
S: ne Cols).

Fic. 4. Superior view of the skull of Turdus a. pallasiz; adult.

Fic. 5. Superior view of the skull of Polioptila caerulea, ad. 9 , New Orleans, La.

Fic. 6. Superior view of the skull of a specimen of Regzlus satrapa, ad. g, col-
lected by Mr. H. K. Coale at Hartford, Conn.

Fic. 7. Superior view of the skull of Psaltriparus plumbeus, ad. 6, New Mexico.
(Probably one of the very smallest passerine skulls of existing birds.)

Fic. 8. Superior view of the skull of Chamea fasciata henshawi ; from a speci-
men collected in California by Mr. F. Stephens.

Fic. 9. Superior view of the skull of Parus inornatus griseus ; ad. § , New Mexico.

Fic. 10. Superior view of the skull of an adult specimen of Parus gambeli.

Fic. 11. Superior view of the skull of Sz¢ta c. aculeata.

Fic. 12. Superior view of the skull of an adult specimen of Zvoglodytes aédon
parkmanit,

Fic. 13. Superior view of the skull of Anchus pensilvanicus; adult.

Fic. 14. Superior view of the skull of a ¢ specimen of an adult Jcteria v.
longicauda, collected by the author at Fort Wingate, New Mexico.

Fic. 15. Superior view of the skull of the Prothonotary Warbler (Protonotaria
citrea) ; ad. g, New Orleans, La.

Fic. 16. Superior view of the skull of Vireo noveboracensis,; adult.

Fic. 17. Superior view of the skull of Ampelis cedrorum ; adult.

Fic. 18. Superior view of the skull of Sayornis nigricans.

Plate V.

PAS SERES.

114 SHUFELDT.

EXPLANATION OF PLATE VI.

Fic. 19. Superior view of the skull of Myiarchus crinitus; adult.

Fic. 20. Anterior aspect of the sternum of AZyiarchus crinitus.

Fic, 21. Dorsal aspect of the pelvis of AZyzarchus crinitus ; the bones figured in
this and figure 20 are from the same skeleton which furnished the skull shown in fig-
ure 19.

Fic. 22. Superior view of the skull of an adult ¢ specimen of Hadia melano-
cephala; New Mexico.

Fic. 23. Superior view of the skull of Cyanocephalus cyanocephalus ; adult.

Fic. 24. Right lateral view of the skull of AZyadestes townsendii, ad. 6; X 2.

Fic. 25. Superior view of the skull of a specimen of Piranga ludovicianus ;

adult.
Fic. 26. Right lateral view of the skull of an adult specimen of Hesperocichla

nevia; X 2.

Plate V1

Fio. 215
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Journ. Morph Vol II.

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NOTES ON THE ANATOMY OF SPEZOTYTO
CUNICULARIA HYPOGAEA.

R. W. SHUFELDT, M.D., C.M.Z.S.

Amone my alcoholic birds that I collected in Arizona and
New Mexico, during the years of 1884 to 1888 inclusive, I find
two very fine specimens of the Burrowing or Prairie Owl (Spe-
otyto), and, as there are certain parts of the anatomy of this re-
markable species, so far as the writer is aware, which have not
as yet received the attention of the ornithotomist, it will be my
aim in the present contribution to offer a few remarks upon the
subject. Naturalists are quite familiar with the two species
of this owl and their geographical ranges ; their habits and nidi-
fication ; and something of their external or topographical anat-
omy; so these chapters in their life-history need nothing from
me here.

TuE PTERYLOGRAPHY.

Upon plucking a specimen of speotyto, we find that it pos-
sesses fwenty-five remiges, and fwelve rectrices. These numbers,
it would seem, agree with the majority of the S¢riges ; but in
the remainder of its pterylography, Speotyto exhibits some
marked departures from the patterns laid down for this order
by so eminent an authority in such matters as Nitzsch.! The
Burrowing Owl, however, agrees in possessing feathers without
an aftershaft, and a tuftless oil-gland, points which essentially
distinguish this group pterylographically. Differing from both
Strix bubo and Hybris flamea, as drawn by Nitzsch, Speotyto has
its head completely feathered, crown, occiput, sides and throat ;
and, furthermore, the anterior and posterior cervical tracts are
notably broad, which is contrary to the rule in these nocturnal
rapacious birds, according to the writer just quoted (see Figs.
1 and 2 of the Plate). About the middle of the neck, the ante-
rior cervical tract bifurcates, each bifurcation passing down to

1 Prerylography, Nitzsch, C. L. (Dr. Sclater’s translation; Ray Society edition,
Lond. 1867). pp. 67-71, Taf. II., Figs. 8-11.

116 SHUFELDT. [Vot. III.

merge with the anterior parts of the continuous humeral and
ventral tracts at the shoulder. A few feathers are also found
at the hinder part of the fossa between the limbs of the os frr-
cula. The ventral tract is divided ; the inner branch being long
and narrow, composed, as it is, of only two rows of contour
feathers. Either row passes almost in a direct line to the outer
margin of the vent on the same side, being strictly defined for
the lower moiety of its course; more diffuse above. On the
other hand, the external branch is very broad, and strongly
marked, as shown in Fig. 2, — its postero-external angle throw-
ing upwards towards the shoulder ‘‘a hook” of large contour
feathers; the area at the outer aspect of the breast between
this latter line and the external branch of the ventral tract is
diffusely feathered with a number of large feathers.

Nitzsch evidently had a specimen of the present species (of.
cit. p. 70), but I am very much inclined to believe that it was
in poor condition, from what he says about it, and the next form
he describes (Strzx pygme@a) ; probably in moult, and kept too
long besides. In any event he failed to note the characters I
have just given for the pterylze of the ventral aspect of this
owl’s body. Anteriorly the legs are pretty well feathered, and
sparsely distributed down-like feathers of no great size cover
the tarsi in front, and become exceeding small as they pass to
the toes on their upper surfaces. It is said that the shanks are
more extensively denuded in the Floridan form of the Burrow-
ing Owl.!

Our subject has its “alar tracts” strongly marked, the
feathers being regularly disposed on their dorsal aspects, con-
sisting of a row of four or five feathers running from each quill
in the direction of the patagium.

Dorsally, the spinal tract shows a conspicuous fork at a point
between the shoulders, as shown in Figure 1 of the Plate, and
a single and more feeble row of feathers connect the apex of
either limb of this bifurcation, with the hinder part of the
spinal tract where it begins again, in the middle line. From
this latter point, it grows stronger and broader once more, and
upon approaching the large papilla of the uropygeal gland, it
surrounds that structure; the caudal region between it and the
rectrices being well feathered.

1 Cougs, E., Key to North American Birds, 2d ed., p. 517. (S.¢. floridana.)

No. 1.] SPEOTYTO CUNICULARIA HYPOGAA. 117

Strong “crural” and “humeral” tracts characterize the
pterylography of Speotyzo, the feathers of the latter being very
long and large. The femoral pterylee are fairly well pronounced
in this owl, and a few scattered feathers may occur beyond it,
as do a few between the limbs of the bifurcation of the spinal
tract, though these latter are inclined to be of the downy variety.

This description goes to show, then, that Speotyto has a ptery-
lography, in some particulars, quite its own, though it is possible
that it may largely agree with such genera in this respect, as
Glaucidium and Micrathene, but I have not specimens of these
at my hand at present, wherewith to compare it. Speotyto has
no ear-valve, and a few delicate feathers are distributed over the
eyelids. As compared with the species of owls described by
Nitzsch, its pterylography is peculiar in the marked and unusual
breadth of the tracts, and in that the head is completely covered
with feathers upon all its aspects.

On CERTAIN STRUCTURES OF THE HEAD.

Seven or eight years ago the writer published a detailed
account of the skeleton of the Owl we now have under consid-
eration, so that we will not be required to touch upon that part
of its anatomy here, or only in so far as some special point
seems to demand it (U. S. Geol. and Geogr. Survey of the Terr.
Dep't of the Interior. ayden’s 12th Ann., pp. 593-626, 3
pls.). Upon removing the teguments of the head, we are to
note that the moderately large eyes of Speotyto look forwards
and outwards, but do not project as prominently as we find
them sometimes in other Strzgide. The nictating membrane is
attached in the usual manner to the antero-superior part of the
eyeball, which latter possesses a deep encasement of sclerotal
plates. As in most Owls, the frontal region of the cranium is
narrow, and the sapraorbital processes are spiculiform, projecting
backwards and a little outwards; to the inner side and apex of
either of these, and to the entire posterior orbital margin, is
attached a dense, fibrous membrane, which covers the globe of
the eye posteriorly, being inserted finally to the cranium in
front of the ear, to the zygoma slightly, and to the under side
of the eyeball, upon which, throughout its extent, it is drawn
tightly down.

118 SHUFELDT. [VOL. III.

In front of the orbital cavity is a spongy bone of some size,
which I described in my memoir upon the osteology of Speotyto
as the /acrymal, and I still take it to be such, and believe the
processes above referred to as the supraorbital processes, to be
developments on the part of the frontal bones. Two skeletons
of nestlings of Bubo virgintanus seem to indicate this: speci-
mens kindly collected for me by Dr. W. S. Strode of Bernadotte,
Ill.; though in these, these processes are exceedingly small.
Among certain Hawks and Falcons the arrangement is very
different ; for in such a species as Fako sparverius, for example,
these processes are very long and conspicuous; but they are
here the true lacrymals, and send down a descending process,
which, in either one, reaches to the maxillary, and articulates
with the entire outer margin of the pars plana. In this little
Falcon no such bone exists as the lacrymal which I have
described for Speotyto, its place being monopolized by this de-
scending limb of the very differently constructed lacrymal in it,
and to which I have just alluded. In such characters as these,
then, we find truly a great difference between such species as
our Burrowing Owl and the Sparrow Hawk.

Removing the vault of the cranium, and breaking down the
walls of the brain-case, here composed of very delicate tables
and abundant open diploic tissue, we find the brain of a form
common to many S¢rigid@,—the cerebral hemispheres large,
smooth, and somewhat pear-shaped, mounting as they do con-
siderably above the rather small cerebellum. The pineal body
is of no great size, while the optic lobes, as well as the optic
tracts, are situated in the deep excavation formed at the bottom
of the cranial casket. All the cerebral nerves, including the
first pair, are of mere thread-like proportions, as soon as they
are given off from the brain mass; and, indeed, the medulla
oblongata is of small calibre compared with the size of the
bird.

An interesting feature is seen at the side of the skull in
Speotyto, where the tendon of the temporal muscle passes
through a foramen, above the squamosal, on the way to its in-
sertion upon the mandible. This arrangement does not exist in
such species as Aszo wilsontanus nor Syrnium nebulosum ; the
former of these, with a very different skull from the Burrowing
Owl, has simply a minute notch devoted to the same purpose;

No. I.] SPEOTYTO CUNICULARIA HYPOGAA. 119

while in Syrnium, with another very dissimilar pattern of skull,
this is shown in a deep groove.

The eyes of Speotyto present nothing worthy of special note,
beyond what we know of these organs among the Owls gener-
ally. We observe, that the optic nerve is of rather small calibre,
for a strigidine bird, while this species affords an excellent type
upon which to study the special musculature of the eye, and the
ever interesting arrangement of the pyramidalis and its tendon.

This specimen has no vomer, its place being superseded by a
median sheet of dense fibrous membrane; and I am strongly
inclined to believe that this bone never ossifies in Speotyto. A
skull of Syrntum at my hand also lacks this element, while in
Asio wilsonianus it is very small, and of peculiar construction,
being sharply pointed in front, hollow, and light, and delicate
throughout. Falconide usually always have a good-sized vomer,
but from what has just been said, we must believe that this is
the exception in the Owls.

Nothing peculiar seems to characterize the internal ear, which
I carefully examined ; nor the tongue, nor the upper larynx.

THE PECTORAL MUSCLES.

For a bird that so seldom seems to resort to flight of any
great extent, Speotyto has its pectoral system of muscles very
well developed.

The fectoralis major, although not very thick, as the sternal
keel is inclined to be shallow, makes up in width, and on the
whole would be considered rather a powerful muscle. It exhib-
its the usual origin and insertion, completely covering the next
two to be noticed.

Of these the pectoralis secundus is also of quite a considerable
bulk, arising from its most usual site on the anterior aspect of
the sternal body, and carina, it shows the bipenniform structure
for which it is notorious, and its tendon passes up through the
tendinal canal, formed by the bones of the shoulder girdle, to
be inserted into the humerus after the common fashion as seen
among birds generally.

A pectoralis tertius of no mean dimensions, but presenting
nothing peculiar, is also found in this Owl, and it completely
covers, in my specimen, the row of sternal articulations of the
hzmapophyses of either side.

120 SHUFELDT. [VoL. III.

CERTAIN MUSCLES OF THE FOREARM AND THIGH.

Professor Garrod has already pointed out that the expansor
secundariorum muscle is absent in the Strigid@ (Coll. Sci. Mem.,
p. 329), and I find Sfeotyto to be no exception to the rule. On
the other hand, the patagial muscles of this family are not alluded
to by him, and here offer several points of interest ; for although
the origin and insertion of the tensor patagit longus are as we
find them in nearly all ordinary birds, the same cannot be said
of the tensor patagit brevis. This latter has its carneous portion
at the shoulder much as we always find it, while its slender
tendon in descending for insertion upon the extensor metacarpt
vadialis longus of the antibrachium, bifurcates at about the mid-
dle of its course, —the inner or proximal slip attaching itself
as usual to the tendon of the aforesaid extensor of the forearm,
and from the point of its insertion a tendon passes by a gentle
curve over the outer aspect of the muscles of the antibrachium,
towards the wrist, and gradually approaches the ends of the
quills of the secondary feathers, into which it finally becomes
inserted at a point about opposite the site of the middle and
distal thirds of the ulna. To return to the remaining slip, the
anterior one, of the bifurcated tendon of the tensor patagiz
brevis, it too becomes inserted into the tendon of the extensor
metacarpi radialis longus at a point situated about half a centi-
metre beyond the insertion of the proximal slip, and in the same
line. It will be interesting to compare this arrangement of the
short tensor of the patagium in other Stvzgzda@, as well as in Rap-
torial birds generally. Before writing out this account of it I
very carefully examined the muscles in question in both limbs,
and found them to agree exactly.

Speotyto lacks the biceps slip to the patagium, as seems to be
the case in all Owls.

Passing to the muscles of the thigh, we find the femoro-caudal
present, and for a representative of this family, rather large ;
the ambiens, the tensor fasciz, the semitendinosus and its acces-
sory slip, and the accessory femoro-caudal are all absent. This
arrangement agrees with the several species of Owls examined
by Garrod, though that distinguished ornithotomist did not ap-
parently examine the present bird, while he did investigate this
point in at least three forms of Azhene.

No. 1.] SPEOTYTO CUNDTCOLAATA HYPOGAA. I2I

Incidently, I may remark here, that in Sfeotyto the main nerve
of the leg is the sciatic; the main artery, the sciatic artery ; and
the main vein, the femoral.

Nowhere in Garrod’s work do I find a place where he paid any
especial attention to the arrangement of the plantar tendons in
the Owls, and he seems to have let this matter rest with his in-
vestigation of four or five species of diurnal Raptores; and of
these he says that “the fleror longus hallucts divides into two
‘moieties opposite the lower end of the tarso-metatarse, one of
which runs to the hallux. The other part is the representative
of the vinculum of the above-mentioned birds; it is peculiar,
however, in that, instead of joining the tendon of the flexor
pervforans digitorum, before it is distributed to the anterior toes,
it mostly runs down to blend with the slip which is associated
with the inner of these (digit 2) only [figures it for 7zxnunculus
alaudarius|.”

“In Geranoaétus aguia and in Polyborus, besides the special
tendon from the hallux-muscle to the second digit, there is a
broad, thin vinculum present, as in Gallus. In the Accipitres
Diurne, the arrangement of the tendons, therefore, differs in
different groups —in Zaza their distribution being quite nor-
mal, that is, as in the first described ; in Polyborus, Haliaétus,
Tinnunculus, and Geranoétus, this condition is combined with a
special tendon to the second digit, which greatly increases its
power of flexion.” (Col/. Sct. Mem., pp. 293, 294-)

Now of the Cathatide, he further adds, in the same place,
that, “the two deep flexors descend beyond the ankle-joint in-
dependently, as usual; after passing which, generally about one-
third down the tarso-metatarse, they blend completely, defore
any slip has been given off. From the conjoined tendon thus
formed the tendons of distribution spring, four in number, one
to the hallux, and others to each of the three anteriorly directed
toes [he here directs attention to his figure of Buceros rhinoceros
to show it], that to the former being generally separated off
before any of the others.” (of. czz. p. 294.)

Upon carefully examining these parts in my specimen of
Speotyto, I find the arrangement a little different even from any
of these; in the leg we find both the flexor muscles distinct, and
their tendons remain distinct to a point about four or five mille-
metres dclow the hypotarsus, where they not only completely

122 SHUFELDT. [Vot. III.

blend, but codssify, forming by their union a strong, straight,
bony rod, which is harbored in a very considerable groove down
the back of the tarso-metatarse, its distal end even extending a
little beyond the free accessory metatarsal of the hallux. Here
it splits up into four nonossified tendinous slips, which are dis-
tributed to the four digits in the usual manner.

The foregoing facts not only prove that the arrangement of
the plantar tendons differs among the diurnal Raptores, but a
still different arrangement is to be found in the American
Cathartide, birds in no way especially related to the former ;
while Sfeotyto goes to show that at least one other peculiar
arrangement of these tendons is to be met with among the
Strigide. This Burrowing Owl has the power of reversing the
hallux, but it is not the normal position of that toe. It may be
as well to add here that in this specimen the tendon of the super-
ficial flexor at the back of the tarso-metatarsus is also completely
ossified.

THE VISCERA AND CERTAIN OTHER STRUCTURES.

An examination of the heart and great vessels reveals the
fact that the first-mentioned organ is comparatively large for the
size of the bird, and elongated rather than of an ovoid shape.
Both carotids are present, and ascend the neck to the head
through the usual canal intended for them on the anterior aspect
of the cervical vertebreze.

Turning to the trachea and syrinx, we find the former for its
lower half, somewhat compressed from side to side, the reverse
of the case in the upper part of this tube. Its rings are
ossified ; not so, however, the ring of the bronchi. Two of the
semi-rings and the pessulus are ossified, and the former open
wide apart posteriorly. But two pairs of muscles appear to be
present, the “ sterno-tracheales,” and the “ tracheo-laterales.”

The “ver is divided into fwo very nearly equal-sized lobes,
joined with each other by a very slender band; and I fail to dis-
cover the presence of any ga/l-bladder.

Of considerable calibre, the wsophagus, including the proven-
triculus, has a total length of 9.5 centimetres, the latter organ
merging gradually into the ovoid and somewhat muscular giz-
zard. This is lined with a firm corneous coat, and the pouch
when opened contained a few large black beetles, being in a

No. 1.] SPEOTYTO CUNICULARIA HYPOGAZA. 123

partly digested condition. The thickest part of the wall of the
gizzard is about 4 millimetres; this is at its posterior aspect,
and quite near the proventriculus. Coues has stated (Key, 2d
ed., p. 498) that the Owls have “short and wide intestines,” but
not so, judging from the specimen before me, the Burrowing
Owl, Speotyto, as in it the intestine is of unusually small calibre,
and very long, measuring from stomach to anus no less than 39
centimetres. Each coeca has a large bulbous extremity though
its pedicle is very slender; it measures 3.4 centimetres, and it
springs from the intestinal tube (at the same point with its fel-
low), 4.6 centimetres above the anal opening.!

Other organs and parts presented in the economy of this Owl
were examined quite in detail by the writer, but nothing of very
great import was discovered, beyond what is common to the
morphology of the group as a whole. The specimen chiefly used
by me in these dissections was extraordinarily fat, especially at
the root of the neck, and overlying the flanks, and lower part of
the dorsum and abdomen.

This Owl, in common with some other S¢riges, has an antero-
posterior foraminal perforation through either coracoid, a fact
which I pointed out in my memoir in the Osteology of the bird,
and I further said there, that “this foramen transmits a branch
of that cervical nerve coming from between the twelfth and
thirteenth cervical vertebre.”? More strictly speaking, I find
upon reéxamination, that although I have given the nerve’s exit
correctly, in reality it is the anterior branch of the brachial
plexus, and after passing through the aforesaid foramen in the
shaft of the corresponding coracoid, from behind, forwards, it
is distributed to the pectoralis secundus muscle, following its
tendon on the aspect next the body of the sternum, while the
minute nerve-fibres branch up among the fibres of the muscle.
This same interesting condition obtains in Aubo virginianus,
and some Hawks of the genus Auzteo.

1 Both the intestine and mesentery in this specimen of Sfeoty¢o had sparsely sprin-
kled over them, sometimes in groups of four or five, and sometimes singly, little ovoid
bodies about the size of No. 10 shot, pure white in color, and having all the appear-

ances of lime-like deposits in the tissues where found.
2 SHUFELDT, R. W., Contributions to the Anatomy of Birds, p. 612.

124 SHUFELDT. [Vou. III.

CONCLUDING REMARKS.

The notes offered in the present paper may fitly be consid-
ered as supplementary to my more extended memoir upon the
Osteology of Speotyto, already alluded to above. I look forward
with pleasure to some day devoting considerable attention to the
American Raptorial Birds as a group, and from what I have
thus far seen of them I have every reason to believe that they
will afford characters of more than usual interest; the Owls, in
particular, are, in many instances, very dissimilar in their skel-
etons and probably so in other systems of their economy. Ana-
tomically, too, the Hawks, Falcons, and Eagles offer much that
requires thorough investigation, and for this work, the writer is
continually employed in bringing together his material.

My researches upon the anatomy of Sfeotyzo, as here set forth,
most conclusively go to show that our American species of Owls
—and there are a number of them — require far more extended
investigations of their pterylography than they have received up
to the present time. Speotyto offers, as I have shown, peculiar-
ities in this regard, not observed by that great investigator of
this subject, Nitzsch, and what I have here described, surely
needs comparison with a number of our S¢vzg@, and I dare say
with forms from the avifaunze of other countries where Owls
occur.

Another matter which needs attention, is to ascertain which
of our Owls possess a vomer, and which do not; it would seem
that this bone of the cranium never ossifies in this Prairie Owl ;
another interesting fact.

Further comparison is needed of the patagial group of muscles
in these birds ; indeed, it would repay the labor to make quite
an exhaustive study of this for the diurnal and nocturnal Rap-
tores, to include the Cathartide. Speotyto,as I have shown, has
peculiarities in this direction also.

Again, the arrangement of the plantar tendons sadly needs
looking into, and thorough comparisons made in the groups to
which I have just referred. What has been brought out in the
present paper, goes to prove that our subject here also affords
structures at variance with the known arrangement of the same
parts in certain diurnal birds of prey.

And so on through the remainder of the economy of Speotyto,

No. 1.] SPEOTYTO CUNICULARIA HYPOGAA. 125

much of which affords, here and there, other suggestive char-
acters. Nevertheless it is very plain to be seen, from all this,
that at the present writing it cannot be predicted with safety
what are the nearest affines of this Owl as indicated by a com-
plete knowledge of strigidine morphology ; but the writer feels
that he has the right to hope that the present outline, with the
salient features in the anatomy of this unique owl, presented as
they here are, may assist to some extent the solving such
problems.

i nk aT D al at] 4
a? wi, hy,
7 i Wt BD

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als

VARIATION, .OF , THE (SPIRALS NERVES. IN THE
CAUDAL. REGION |\OR (GE (DOMESTIC
PIGEON.

JAMES I. PECK, A.B.

OnE of the most conspicuous of the variations in the internal
structure of the common domestic pigeon, is that which affects
the number of the vertebrze in the caudal region. These ordi-
narily vary from five to eight between the sacrum and coccyx ;
and it was the purpose of this work to determine whether the
pairs of spinal nerves vary in the same ratio, or whether they
remain constant in number and position of exit from the verte-
bral canal, without reference to the number of vertebra them-
selves.

The methods were first by dissection, and the accuracy of the
results so gained was then tested upon the same and other
specimens by cutting sections. Before dissecting, the whole
caudal region was taken from the bird, the muscles and con-
nective tissues removed from one side so as to determine accu-
rately the number of free vertebra, but left upon the other side
so as to leave all spinal nerves intact. The part was then placed
for a fortnight or more in an aqueous solution of picric acid
until the nerves were hardened and the vertebrae somewhat
decalcified, so that their processes could be cut easily with a
sharp scalpel; the specimen was then pinned out under water,
the neural arches cut away, and the cord and pairs of nerves so
exposed were traced out under a lens with bent needle points.
A considerable number of birds were dissected in the fresh
state also, but with less certainty about the last nerves. For
cutting sections, a much longer decalcification in picric acid was
required before the centra of the vertebrae would become suf-
ficiently pliable, and a maceration in a ten per cent solution of
nitric acid for two or more days was found to be more expedi-
tious. Borax carmine and hzmatoxylin were used for staining,
and the material imbedded in paraffine.

128 PECK. (VoL. III.

In most cases the dove-cote pigeon possesses six free caudal
vertebrz and the coccyx; but not infrequently specimens are
found with seven free vertebrz, the fan-tail with eight or seven,
while sometimes cases are found with as few as five. In a paper
on the gallinaceous birds,! W. K. Parker says: ‘I do not set so
much value on the number of caudal vertebre, as the last isa
series, and the tail is very apt to vary in the number of those
which shall be swallowed up in the terminal piece. The sacral
are easily distinguished from the caudal in these birds, as even in
the pigeons the caudal are no longer pneumatic; that is a better
character even than the coalescence of a vertebra with those
that precede it.” Thus in the pigeons the variability extends
not only to members of different orders of birds, but is marked
in the same species and may be more or less fixed by selection,
as in the fan-tails, which ordinarily have eight or nine caudal
vertebrz, according to Darwin,? and possibly ten. The coccyx
from the very nature of its composition is of varying length and
curvature ; these features being determined perhaps by the more
or less complete fusion of a vertebra to its anterior end, while
the connective tissue which attaches to it and bridges over from
it to the adjoining vertebrz, forms a convenient medium of ossi-
‘fication tending toward the obliteration of the last and smallest
vertebra in the compact mass of connective tissue for the inser-
tion of the rectrices. But it can hardly be said that the num-
ber of free vertebrze depends upon the freedom or fusion of the
last one with the coccyx, for in this case we should expect to
find a long coccyx following a short series of caudal vertebre,
and a short coccyx where the most vertebrz are free from it;
whereas the facts would indicate that a large number of vertebrz
is followed by a longer coccyx, so that in the cases having seven
or eight free vertebrz the coccyx is longer than in those possess-
ing five or six (cf. cin Figs 1-4), suggesting some other cause
for the lengthening of the whole region, as a result of which
more vertebrz are left detached from the terminal piece; so
that as the whole region is lengthened or shortened the coccyx
lengthens or shortens in about the same ratio. But it is often
quite difficult to determine the exact length of the coccyx, on
account of its imperfect union with the preceding vertebra.

1 Transactions of the Zovlogical Society of London, Vol. V., p. 198.
2 Animals and Plants under Domestication, Vol. I., p. 205.

No. 1.] SPINAL NERVES OF THE DOMESTIC PIGEON. 129

In close relation to the varying vertebrz stand the spinal
nerves. The dorsal ganglion is very prominent, being smaller
in size and farther from the cord in the most posterior pairs of
nerves. Shortly beyond the ganglion the nerve branches, — one
branch sinking below the lateral process of the vertebra and
supplying the muscles beneath, the other and smaller running
backward in the muscles dorsal to the vertebre. In the ordi-
nary dove-cote pigeon, of six free caudal vertebrae, there would
be seven intervertebral spaces in which the outgoing spinal
nerves would lie if they existed (Fig. 2, s:-s;); but on account
of the mass of connective tissue which invests the coccyx and
terminal vertebrze, for the attachment of muscles and quills of
the large tail-feathers, the terminal segments of the vertebral
column seem to have lost their independent action and to have
become more or less anchylosed ; the cord within is degenerated
into a large filum terminale which gives off no nerves posterior
to the fifth space, Fig. 2, ss. Thus the dissection of the com-
mon birds, represented in Fig. 2, would ordinarily reveal a series
of six free caudal vertebrae and seven intervertebral spaces, and
a continuous series of paired spinal nerves (7-75), leaving the
neural canal between these vertebrae as far backward as the
fifth space, s;; leaving the last two spaces without nerves, while
the cord is continued on far into the coccyx as a large filum
terminale, gradually diminishing in size until it runs out. The
nerve roots are seen in the dissected cord to originate some dis-
tance anterior to the point of exit. A bird having only five free
caudal vertebrze is comparatively rare, and yet the same relation
between nerves and vertebrze seems to exist as in the more
common form with six. Thus the dissection represented in Fig.
1 shows a series of only five free vertebra, six spaces (S:-Ss),
and a continuous series of nerves, which stops short, however,
of the last two spaces as in the former case (Fig. 2), thus show-
ing a reduction of the cord in accordance with that of the bony
investment. The filum, as before, is continued far into the
coccyx. The vertebree in this specimen were all very distinctly
made out, as there was no imperfect union either withthe sacrum
or with the coccyx. A variation by the increase of the number
of free vertebrae to seven is more commonly met with. Darwin
states that this is the normal constitution of the rock pigeon ;?

1 Animals and Plants under Domestication, Vol. 1., p. 205.

sap or PECK. [Vot. III.

and in two of the fans used in this work there were only seven
caudal vertebre actually free, the eighth being imperfectly anchy-
losed with the end of the coccyx, and in several other ordinary
birds the same number obtained. No especial reason could be
given for this increase in the series, since the birds did not
differ materially from the others in size, nor were any of the
variations apparently more common in one sex than in the
other, although two birds with seven vertebrae and one with six
“vertebrae were male, four with six and the one with five verte-
bree were female, all having been taken at random from the
belfry of a church. But the ratio of variation was much greater
in this lot than is the rule, for in the thirty-odd specimens exam-
ined, there was no other case of five vertebrze found, and a
smaller percentage with seven vertebrze would usually be found
than occurred in this lot of six birds. So also a large white
male fan with twenty-six tail-feathers was provided with only
seven actually free vertebra, the same number as an ordinary
common male bird possessed. But the dissection of such a
specimen with seven free vertebree shows again that the series
of nerves is coincident with the series of vertebrze between
which they are given off, as far backward as to leave only the
last two spaces without nerves (Fig. 3, si-5s, -%,), adding
me to fill ss upon the addition of an ss beyond s; The most
remarkable development of the caudal region is naturally found
in the fan-tail, since the efforts of selection have been directed
toward this part of the body in inducing a wide expanse of tail-
feathering. The usual number of eight vertebrze was found,
but in two cases the eighth, or last, was imperfectly anchylosed
to the coccyx, so that although the neural arch was plainly sep-
arate, yet the body of the vertebra was immovably united with
the coccyx. A dissection of a specimen with eight actually free
caudal vertebrz is represented in Fig. 4, where by the further
addition of another vertebra the intervertebral spaces become
nine (s;-s5,) in number ; and here too another nerve, ,, appears in
57, augmenting the series so as to keep z constant with s, ze.,
the last two spaces only in the series of vertebrz are left with-
out nerves as in the other cases.

Thus far it will be seen from a series of dissections that the
supply of nerves from the cord is constant with the series of
vertebra ; a change in the latter is followed by a corresponding

No. 1.] SPINAL NERVES OF THE DOMESTIC PIGEON. 131

change in the former. But cases are often found in dissection
which show that the supply of spinal nerves is not always con-
stant in this relation to the number of vertebrz, so that nerves
may appear in the next space behind, in one of the two that are
often, if not ordinarily, left vacant. Thus Fig. 5 represents
such a dissection where a new term %, is introduced into s, of a
series of six free caudal vertebre. A comparison with Fig. 2
will show that the nerve supply has undergone less reduction by _
one pair of spinal nerves proceeding into s,; or that the nerve
supply is here better developed than in other cases. The same
variation was met with in dissections of specimens with seven
free caudal vertebrz, so that another figure might be drawn in
all respects similar to Fig. 3 with the exception that an x, would
appear in s; (cf. Fig. 3). This was made out in a large white
male fan with seven actually free vertebrz, and no less distinctly
in a common dull-colored male bird of the same number. The
other cases of seven vertebrze that were dissected proved to be
as represented in Fig. 3. This occurrence of the extra pair of
nerves is of course merely the fulfilling of ordinary conditions
of the spinal column, which here may or may not take place,
just as the last vertebrze in the series may or may not be articu-
lated with the coccyx, instead of being ossified with it. And
there is no reason to suppose that the very last space might not
in some cases be furnished with nerves also, although there is no
evidence of this occurring in the many specimens examined.
Sections of the vertebral column and the cord in place show
the arrangement of the investing membranes, the relative size
and structure of the filum terminale, the lumen of the cord, and
the exit of the nerves. The dura mater investment extends to
the extremity of the vertebral canal, which runs at least three-
quarters of the length of the coccyx. This membrane contains
blood-vessels running in it, one of which passes up into the pia
mater, in which it may be traced far forward ; it is in connection
with this that the pia mater and the end of the filum first appear,
some twenty sections anterior to the end of the spinal canal.
The lumen of the cord itself first appears in the filum within five
or six sections of the end. Thus the relations of the pia mater,
the blood-vessel, and the lumen of the cord are shown in Fig. 6;
—the section being much magnified, so that the space between
the dura mater and the pia mater is not brought into the field.

132 | PECK. [Vot. III.

The central lumen or canal of the cord is seen to be very promi-
nent at this point, and is surrounded by a dense row of nuclei,
which are those of the epithelium lining the canal. The exact
nature of the other mass of nuclei that are collected within the
investing membrane is not easy to determine. Some of them are
quite large and show a distinct nucleolus, a few may be from the
gray matter, and some connective tissue nuclei. A neuroglia
also exists to some extent, — enough to form a kind of matrix
for the nuclei. As the filum passes forward, the same general
structure is seen, but its actual size is much increased, the
nuclei becoming fewer, and the neuroglia consequently more
distinct. Thus Fig. 7 represents a section taken beyond the
coccyx on the posterior face of the last free vertebra; z.e., in the
anterior part of s, in Fig. 2. The filum has increased in size,
and the lumen is lined by a row of columnar nucleated cells,
while in the other parts the nuclei are less thickly distributed
than in the former section. The dura mater investment lines
the neural arch cavity, and the pia mater closely invests the
filum itself, being thicker upon the lower side. It is from
this lower side of the pia mater investment that connective
tissue processes are given off which go out to the dura mater
and serve to support the cord in place. In this region they
are not numerous, but they are seen in serial sections attached
to the dura mater and to the pia mater; they are sometimes
oblique, and are then to be carefully distinguished, when viewed
under low powers, from nerves lying in the cavity. Blood-
vessels are now abundant in the dura mater, and smaller ones
in the pia mater. Passing forward into the next anterior
space (ss, Fig. 2) and selecting a section well forward so as to
include the position of outgoing nerves, the structures take the
form represented in Fig. 8. The connective tissue arch between
the including vertebrae becomes somewhat broken through in
part, and allows the exit of blood-vessels that pass to parts be-
neath ; but in this, as in all the sections of this vertebra, —cut-
ting anteriorly, —no pair of nerves lying near the cord is cut.
The lumen of the cord —still lined by the nucleated cells — is
becoming relatively smaller, the size of the filum terminale itself
is increased, and together with the investing membranes takes
on more of the characters of the cord proper. A section in the
next intervertebral space (s;, Fig. 2) includes the last pair of

No. 1.] SPIVAL NERVES OF THE DOMESTIC PIGEON. 133

spinal nerves (#;, Fig. 2) as they leave the vertebral column:
In a series of sections running anteriorly these nerves are at
first, of course, cut diagonally at some distance from the cord
itself, since they enter the neural canal obliquely ; and a section
at that point shows them near to the cord, lying within the neu-
ral arch (Fig. 9, 2). Passing within the neural canal, the nerve
does not immediately become attached to the cord, but runs for
a time quite above it in the dura mater investment ; finally it
comes to lie within the latter, and passes more anteriorly into
the pia mater close to the cord, in which it is contained until all
the fibres have passed into the cord itself, — some distance there-
fore anterior to the place of exit. So that. while cutting through
one of the more anterior vertebrze the nerves destined to pass
out in the next posterior space are found lying beside the cord,
yet these pass into the structure of the cord before the exit of
the next anterior pair of nerves from the spinal canal; ze.,
only one pair of nerves lying parallel with the cord will appear
in any given section. And so the “brush-like” arrangement of
the nerves from a definite end of the cord, as is found in mam-
mals, is not strictly the case here, although the point of attach-
ment of each pair of caudal nerves to the cord is anterior to
their place of exit from the vertebral column, as in the former
case. No definite region could be determined as the place
where the gray matter of the cord begins. It seems rather to
accumulate insensibly—in sections running forward — about
the central lumen of the cord until the cornua take their char-
acteristic shape. Cells belonging to the gray matter are present
doubtless in greater or less quantities throughout the filum, so
that the latter seems to be merely a continuation of the cord
that does not give origin to spinal nerve roots. There seem to
be no definite tracts in which these ganglion cells are laid, but
such are definable a little anterior to the elongated origin of the
roots of the last pair of nerves. The ganglion upon the dorsal
root of the more posterior pairs of caudal nerves is situated far-
ther from the neural canal, and is also much smaller, but in the
more anterior parts of the caudal region the ganglion lies in the
intervertebral space, and sections pass through it at a very slight
angle. Such a section taken in s, or s, shows the structure of
the ganglion lying in the space, as in Fig. 10. Upon the right
side of the figure the proximal part of the ganglion is cut

134 PECK. [Vot. III.

through, showing its extraordinary length and size, and the
large cells interspersed with fibres. These cells are very large,
sometimes measuring 36, in length, and 24 in breadth. On
account of the obliquity of the plane of section, both the dorsal
and ventral roots are shown upon the left side of the figure
before their union, showing again the great length of the gan-
glion structure upon the dorsal root of the more anterior caudal
nerves.

Owing to the difficulties of distinguishing the nerves that
might occur in the last two spaces in the dissections, on account
of the abundance of connective tissue that obscures them, it is
possible that a great number of specimens devoted entirely to
sections might show a larger proportion of cases where nerves
occur in the anterior one of these spaces. But the results are
the same in any case, namely, that by the lengthening of the
caudal series of vertebra, the nerve supply from the cord fol-
lows in the same, if not an increased ratio; and that the series
of nerves is always continuous, z.é., consecutive. As there are
different degrees of anchylosis between the last vertebre and
the coccyx in different specimens of the same flock, so are there
different degrees of nerve supply from the cord. And especially
as the last vertebra is most variable, so is the nerve in this space
preceding it. Indeed, one series of sections was made in which
there seemed to be only a single nerve leaving the cord in the
last space but one, its fellow being wanting on the other side;
and one specimen had the same appearance in dissection. The
last vertebra is often found with its neural processes as free as
any of the others, but with its centrum firmly anchylosed with
the coccyx of which it thus forms a part. Sections also show
that the filum terminale is a structure of some importance and
complexity, and runs far into the coccyx, carrying the two in-
vesting membranes, the dura mater and pia mater, the former
of which extends to the extreme end of the spinal canal; and
that the lumen of the cord persists very plainly to the end,
where it closes ; also that there is no “cauda equina”’ exactly
comparable with that which is found in mammals, since the
nerves originate from the cord at considerable intervals from
each other; and finally, sections give added evidence to the
ready variability of the central nervous system in correlation
with other parts.

No. 1.] SP/VAL NERVES OF THE DOMESTIC PIGEON. 135

This work was suggested, and to a great extent directed, by
Prof. S. F. Clarke, for whose aid in procuring material, and
many laboratory facilities, and for whose kindness, I am much
indebted.

BIOLOGICAL LABORATORY, WILLIAMS COLLEGE, June, 1888.

136 PECK.

EXPLANATION OF PLATE VIII.

The dissections are all drawn to a scale.

Fic. 1. Five caudal vertebrae. The letters s,-s, indicate the intervertebral spaces.
The letters ,-7, denote the nerves as far as they occur in the spaces. ¢, the
coccyx.

Fic. 2. Six free caudal vertebree. Letters as before, showing the addition of
another vertebra, and so of s,, with the corresponding addition of 7;.

Fic. 3. Seven free caudal vertebrze,— with corresponding addition of s,, followed
by the occurrence of another pair of nerves, 7.

Fic. 4. A fan-tail with eight free caudal vertebrze, increasing the intervertebral
spaces by 5s, ; another pair of nerves now found in space seven.

Fic. 5. Showing the ordinary number of six vertebrae, and spaces s,-s, (compare
with Fig. 2), but the usual number of nerves is increased to 7., which does not occur
in Fig. 2. A similar variation might be indicated for Fig. 3 with its seven vertebrze.

The sections, except Fig. 6, were drawn with an Abbé camera, Zeiss objective A,
and ocular 2.

Fic. 6. A section of the filum terminale taken very near its extremity in the
coccyx. /.m., the pia mater investment; /., the lumen surrounded by nuclei; 4.v., the
blood-vessel. This section was drawn with objective D, ocular 4.

Fic. 7. Section taken in s, (of Fig. 2), showing that no nerves leave the cord in
this space. .a., neutral arch of vertebra; 7, filum terminale; .7., pia mater; d.m.,
dura mater; a.z., adipose tissue.

Fic. 8. Section taken in s, (Fig. 2), showing the absence of outgoing nerves.
n.a., neural arch of vertebree; f, filum terminale; a.¢., adipose tissue.

Fic. 9. Section through s, (Fig. 2), showing the presence of the last pair of out-
going pair of spinal nerves. 2.a., neural arch; #., nerves cut obliquely; 7, filum
terminale.

Fic. 10. Cross-section of cord in place taken more anteriorly, — in 5s, or s,,—
including a longitudinal section of the long ganglion, g., on the dorsal root of the
nerve; #.q@., the neural arch of vertebrze; 7.7., pia mater; @.., dura mater; /, the
lumen of the cord; g., the ganglion. The section, being taken a little obliquely,
shows the two roots of the nerve upon the left side before their union. On the right
side the ganglion cells are shown in the outgoing dorsal root.

AMGEN & co. ty P .

Peck del.

Volume III, September, 1889. Number 2.

JOURNAL

OF

MO R Finn CGY":

THe MECHANICAL "CAUSES, OFP THE DEVELOP-
MENT OF THEE Akh BAR TS° OF
THE MAMMALIA.

BE. DNCOPRE:

ALTHOUGH three-quarters of a century have elapsed since
Lamarck formulated the causes which produce variation in
organic beings, but little has been done towards tracing the
immediate action of those causes. The father of organic evolu-
tion ascribed some of these modifications of structure to changes
in the environment, some to the motions of the organic being,
and others to both combined.! Spencer in 1865? devoted a short
chapter to the effect of motion in producing variations, and speci-
fied the mechanical effect of flexure in producing segmentation
of the vertebral column. The present writer, in 1871,° insisted
on the importance of motion as a factor in determining growth,
and in 18724 approached the subject more definitely in the fol-
lowing language: ‘The first physical law is that growth force
... must develop extent in the direction of least resistance, and
density on the side of greatest resistance.” In 1877 Ryder fur-
ther applied the principle of motion to the origin of structural
changes in the feet of Mammalia, in the following language :°

1 Philosophie Zovlogique, Chap, VII., 1809; translation in American Naturalist
for 1888.

2 Principles of Biology, I1., pp. 167 and 195.

3 Proceedings of the American Philosophical Society, p. 259; Origin of the Fittest,
1887, p. 210.

* Penn Monthly Magazine ; Origin of the Fittest, 1887, p. 30.

° American Naturalist, 1877, p. 607,

138 COPE. (Von. Ti,

“1. That the mechanical force used in locomotion during the
struggle for existence has determined the digits which are now
performing the pedal function in such groups as have undergone
digital reduction. 2. That where the distribution of mechanical
strains has been alike upon all the digits of the manus or pes,
or both, they have remained in a state of approximate uniformity
of development.” In the same year, in discussing the origin of
the great development of the incisor teeth in the Rodentia,}
Professor Ryder, in summing up, ventured “the reflection that
the more severe strains to which they were subjected by enforced
or intelligently assumed changes of habit, were the initiatory
agents in causing them to assume their present forms, such
forms as were best adapted to resist the greatest strains without
breaking.” In 1878 the writer? advanced the following propo-
sition: ‘Change of structure is seen to take place in accordance
with the mechanical effect of three kinds of motion, viz., by
friction, pressure, and strain.” Inthe same year Professor Ryder
went into a discussion of the specific application of strains in
the evolution of the dental types of the Diplarthrous Ungulata,
and prepared the field for work in the Rodentia and Proboscidia.
In 1879 the writer gave mechanical reasons for the reduction of
the sectorial teeth of Carnivora to one, and for its present posi-
tion in the jaws. In 1881 the writer® described the specific
action of impacts and strains in the production of the existing
characters of the articulations of the limbs in the higher Mam-
malia. In 1887 the same subject, together with that of the
mechanical origin of the characters of the molar teeth, was more
fully investigated in a paper on the Perissodactyla.6 In 1888
the writer published a paper on the mechanical origin of the
sectorial teeth of the Carnivora,’ one on the mechanical origin
of the peculiar dentition of the Rodentia,’ and a third on the
mechanical origin of the dentition of the Amblypoda.? In 1889

1 Proceedings Philadelphia Academy, 1877, p. 318.

2 American Naturalist, 1878, January; Origin of the Fittest, p. 354.

3 Proceedings Philadelphia Academy, 1878, p. 45.

4 American Naturalist, March, 1879.

5 American Naturalist, April and June, 1881.

6 American Naturalist, 1887, pp. 985, 1060. ;

7 Read before the American Association for the Advancement of Science, New
York, 1887, p. 254. 8 American Naturalist, January, p. 3.

9 Proceedings of the American Philosophical Society, 1888, p. 80.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 139

the writer discussed the mechanical causes of the structures of
the elbow and other joints, in the Artiodactyla, and the origin
of the peculiar intervertebral articulations in that order.! This
enumeration covers, so far as I am aware, the work done in this
field. A good deal of it has been tentative, while to other por-
tions of it considerable precision and conclusiveness may be
granted.

At the present time we are in a position to understand what
the structural changes are, which the Mammalia have gradually
acquired through the operation of causes long continued through
geologic time. In other words, we are now, thanks to verte-
brate paleontology, in possession of the phylogeny of most of
the lines of Mammalian descent. We are thus able to distin-
guish between primitive characters and characters of degener-
acy. We can understand the origin and progress, and also the
decadence, of structural characters. The more my attention has
been directed to the facts thus presented, the more convinced I
have become that, in the language of Lamarck, it is the habit
that has given rise to the structures of animals, and not the
structures which have forced animals to adopt their special
habits.

In the following pages the salient characters of the skeleton
and of the dentition of the Mammalia are examined, and the
attempt is made to discover in the light of the descent traced
by paleontology, the mechanical causes for their existence. It
is believed that in a considerable proportion of instances this
attempt has been successful; while in others a tentative stage
only has been reached. The intelligent reader will be able
to determine to which category any given discussion may be
referred.

The position of the Post-Darwinians is clearly set forth in an
abstract of a lecture delivered by Prof. E. Ray Lankester, at
the London Institution, which appears in Nature of February
28, 1889. Professor Lankaster declares that the error of La-
marck (and consequently of the Neolamarckians) consists in the
assumption that acquired characters can be inherited. He says:
“Congenital variation is an admitted and demonstrable fact ;
transmission of congenital variations is also an admitted and

1 American Naturalist, March, 1889.

140 COPE. [Vot. III.

demonstrable fact. Change of structure acquired during life —
as stated by Lamarck —is also a fact, though very limited. But
the transmission of these latter changes to offspring is not
proved experimentally ; all experiment tends to prove that they
cannot be transmitted.” Two inferences may be derived from
these statements. First, the author of them does not believe
that the so-called congenital variations can be or have been
acquired ; second, that he has no hypothesis to offer in explana-
tion of the origin of congenital variations. These positions
exclude another inference, which nevertheless may be derived
from other propositions embraced in the abstract of the lecture.
He says, with Lamarck, that ‘change of structure acquired
during life is also a fact,” and also that “all plants and animals
produce offspring which resemble their parents on the whole.”
But in spite of these statements we are to believe that if a plant
or animal acquires a useful addition to or modification of its
structure during life, this is the particular variation which will
not be transmitted. Since the modifications acquired by use
during life are necessarily useful, it seems that according to the
Post-Darwinians, the only way of acquiring useful variations
known to us, is excluded from the process of organic evolution.
To say the least of it, probabilities are severely taxed by such
a position as this.

But we say further, with Professor Cunningham, that were
this hypothesis true, there would have been no evolution. If
acquisition during lifetime is to render a character non-trans-
missible, the continued growth of a single character by accre-
tions during successive generations through geological ages
could not and ought not to occur. Each generation should
begin where its ancestors began in the matter of useful charac-
ters, or those acquired by use, so that there could be no‘accu-
mulation or development of such characters. The influence of
the environment, as well as that of the energies of the living
being, would be incompetent to develop more in a given gen-
eration than that generation could acquire in its single lifetime.
How then can evolution account for the law so beautifully dis-
played by paleontology, of the gradual modification of parts
through long geologic ages, towards given ideals of mechanical
perfection? How can we account for the gradual perfecting of
the articulations of the internal and external skeletons of those

No.2.) SHE HARD PARTS OF THE MAMMALIA. 141

»)

which possess them? Not only is no explanation offered by the
Post-Darwinian school, but such progress is, under their hypoth-
esis, impossible. It is an explanation of odscurus per obscurtus.
But we are still of the opinion, in spite of Weissman’s theory to
the contrary, that so long as the germ plasma is subject to
nutrition, it is subject to influences occurring during the adult
life of an animal, and it would be an exception to all the other
tissues were it not so.!

The ground covered by the present essay is only that which
paleontological discovery has brought fairly within reach. The
history of some parts of the skeleton in various types is yet
unknown, especially as regards their function in extinct forms.
The solution of these problems must be left for future research.

It has been found that in all instances where it has been prac-
ticable to observe living animals, explanations of puzzling struc-
tures were found in some peculiar habitual movement which they
exhibit. In this investigation I have been, therefore, greatly
aided by the Zodlogical Garden of Philadelphia and its able
superintendent, Mr. Arthur E. Brown. I have also derived
considerable assistance from the extensive series of photographs
of animals in motion, by Muybridge, issued under the auspices
of the University of Pennsylvania; and the analysis of these
motions in the accompanying text by the distinguished anato-
mist, Dr. Harrison Allen.

It must be mentioned at the outset that bone-tissue is plastic,
especially in the living state, and in time moulds itself upon
resisting surfaces. The more spongy tissues modify their form
in accordance with denser, when in contact. As Professor Ryder
has remarked, even a substance as rigid as the enamel of the
teeth yields its form to continued pressure and strain, as not
less rigid rocks and stones are known to do. But in a living
tissue like bone, the effect of such application of energy is evi-
dently much greater than in any equally rigid non-living body.
The metabolism of nutrition is clearly a most important factor
in the production of the results, rendering the transfer and loca-
tion of building material possible, which unassisted impacts
and strains could not accomplish.

1 4merican Naturalist, March, 1889.

142 COPE. [Vou. Til.

INTRODUCTORY REMARKS ON THE PHYLOGENY OF THE
MAMMALIA.

The following scheme expresses the classification of the Mam-
malia as adopted by the writer. While it expresses the natural
groupings and affinities, it is defective in that some of the
definitions are not without exceptions :

I. An interclavicle ; a large coracoid bone articulating with the sternum
(Prototheria Gill).
Marsupial bones ; fibula pene with ne end of
astrapalus.. - =. . . « I. Monotremata.
II. No “aside: Erricoid: a dal process codssified vote the scapula
(Eutheria Gill).

a. Marsupial bones (generally); palate with perforations; (vagina
double; placenta and corpus callosum rudimental or wanting ;
cerebral hemispheres small). (Didelphia de ae

But one deciduous molar tooth . . . . . . 2. Marsupialia.
aa. No marsupial bones; palate eeneally Erne (ene vagina; pla-
centa and corpus callosum well developed). (Monodelphia de Bl.)

B. Anterior limb reduced to more or less flexible paddles ; posterior
limbs wanting (Mutilata).

No elbow joint; carpals discoid, and with the digits separated by cartilage ;

lower jaw without ascending ramus . . . . . . 3. Cetacea.
An elbow joint; carpals and phalanges with normal articulations ; lower jaw
with ascending ramus. . . Fad) Jip ViAZee

BB. Anterior limbs with flexible joints ane) distinct digits ; ungual pha-
langes not compressed and acute at apex! (Ungulata ”).
y. Tarsal bones in linear series ;? carpals generally in linear series.

Limbs ambulatory; teeth withenamel. . . . . . >. 5. Vaxeopoda.
yy. Tarsal series alternating; carpal series linear, or reversed diplar-
throus. :
Cuboid bone partly supporting navicular, not in contact
with astragalus . . . 5 : wa Va aie, Braobasceae

yyy. Both tarsal and eee series more or less alternating; the inferior
row inwards.
Os magnum not supporting scaphoides ; cuboid supporting

astragalus ; superior molars tritubercular . . . . 7. Amblypoda.
Os magnum supporting scaphoides ; superior molars quad-
rituberculané 4 Ue wees ei eel. oo es Ae eran
1 Except the Hapalidee. 2 Lamarck, Zodlogie Philosophigue, 1809.
3 Except in Dendrohyrax. * Except Pantolestes.

5 This order includes the suborders Perissodactyla and Artiodactyla. It is the
Ungulata of some authors.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 143

BBB. Anterior limbs with flexible joints. Ungual phalanges compressed
and pointed ! (Unguiculata).
§. Tarsal and carpal bones generally in linear series.
e. Teeth without enamel; no incisors.
Limbs not volant; hemispheres small, smooth; mastica-

fom orthal «.) s.r eed es...) Qs Egentata.

ee. Teeth with enamel; incisors present.
No postglenoid process; mandibular condyle round;

limbs not volant; hemispheres small, smooth; masti-

Gition proal. 2. )-. - 2: queen rete . 10. Rodentia.
Limbs volant; hemispheres small, smooth . , . » Ut. Chivoptera:
A postglenoid process; mandibular condyle transverse ;

limbs not volant ; no scapholunar bone?; hemispheres

small, smooth; mastication orthal . . . 12. Bunotheria.
A postglenoid process; limbs not volant; with a scapho-

lunar bone; hemispheres larger, convoluted; masti-

eauionOrthal. ../ . 3. <aeet eee eee ese (a: 5 E3. Carnauprya:

88. Tarsal and carpal bones alternating.
Fore limbs prehensile; mandibular condyle transverse ;
feeua. with enamel. .- 2) eae ee TA Ansylopada.

Paleontology has cleared up the phylogeny of most of these
orders, but some of them remain as yet unexplained. This is
the case with the Cetacea, the Sirenia, and the Edentata. The
Marsupialia can be supposed with much probability to have
come off from the Monotremata, but there is as yet no pal-
eontological evidence to sustain the hypothesis. No progress
has been made in unravelling the phylogeny of the Cetacea
and Sirenia. The results attained by the study of the paleon-
tology of the other orders may be summarized as follows :—

First. It is probable that the common ancestors of the pla-
cental and implacental lines of Mammalia are known to us in
some of the types of the Jurassic period. Whether they were
marsupial in the sense of possessing an external pouch for the
young or not, is immaterial. They were probably marsupial in
brain characters, in the structure of their reproductive system,
and in the absence of placenta. To this source the existing
polyprotodont marsupials may be traced, through such forms as
Myrmecobius. The Multituberculate type has a cotemporary
history, and one distinct from that of the Polyprotodontia, and
its ancestry has not been yet discovered. Their earliest forms

1 Except Mesonyx and some Rodentia and Edentata.
2 Except Erinaceus.

144 COPE. [VOE. IEE.

(of the Jurassic and Triassic) are already highly specialized.
They probably represent the Monotremata of their time.

Second. The immediate didelphian ancestors of the mono-
delphous Mammalia have not yet been certainly discovered. In
the oldest of the latter (of the Puerco epoch) numerous points
of approach to the insectivorous Jurassic forms occur, especially
in consequence of the prevalent trituberculy of the molars in
both epochs.

Third. The phylogeny of the clawed group has been traced
back to a common ordinal form which has been called the
Bunotheria. We trace the Carnivora back to the creodont sub-
order of the Bunotheria; the Rodentia to the Tillodont; the
Edentata possibly to the Tzeniodont, and the Insectivora are
themselves coextensive with the history of the placental series.
The Ancylopoda only have undergone the alternation of the
carpal and tarsal bones, which obtains in the Diplarthrous
Ungulata.

Fourth. The phylogeny of the hoofed groups carries us back
to the order Condylarthra, the hoofed cotemporary of the
Bunotheria. The even and odd toed hoofed mammals are
traceable back to the Amblypoda, whose oldest representatives
are the Pantodonta of the Puerco. The Proboscidia and Hyra-
coidea come directly from the Condylarthra. Moreover, the
phalanges of the lemurs are not distinguishable by any impor-
tant characters from the hoofs of the Hyracoidea and Condy-
larthra. Not only this, but the structure of the foot in these
three groups is identical in regard to the mode of articulation
of the first and second rows of the tarsal and carpal bones.

fifth. The characters of the feet of the Condylarthra agree
with those of unguiculate placental Mammalia, and bind the
two series together; a very slight modification only being
necessary in the case of the foot of the Pantodonta. The syn-
thesis of the Ungulate and Unguiculate lines is accomplished
by exceptions to the characters which define them. Thus the
hoofs of Pantolambda (Amblypoda), Periptychus (Condylarthra),
and Mesonyx (Creodonta) do not differ by any marked charac-
ter. Claws occur in the Hapalidz of the quadrumanous line,
and the ungues of some Rodentia and Edentata (Glyptodon) are
absolutely intermediate between the hoofs and. claws. The
Bunotheria with tritubercular molar teeth are then traceable

No. 2.] THE HARD PARTS Of WHE MAMMALIA. - 145

to Condylarthra with tritubercular teeth, of which many are
known from the Puerco beds, or vice versa; and the quadri-
tubercular forms from corresponding quadritubercular Condy-
larthra, of which many are known, or vice versa.

Szxth. The anthropoid line may be traced directly through
the lemurs to the Condylarthra. The changes which have
taken place in the skeleton are slight, and consist among other
points in a rotation of the first row of carpal bones outwards
on the second row, in the anthropoid apes and man, similar to
that which has occurred among the Ungulata, but it has not
become so pronounced.

As a result we get the general phylogenetic scheme as shown
on the following page.

In this diagram, divisions of greater and lesser rank are
mixed, so as to display better some of the relationships. Thus
all the divisions whose names stand on the right side of the
middle vertical line are unguiculates ; and those on the left side
of the line, excepting Sirenia and Cetacea, are ungulates. The
three names in the middle vertical line are those of the sub-
orders of the Taxeopoda.

In the table! (p. 147), the history of some of the diagnostic
characters of the Mammalia is shown, in connection with the
passage of geologic time. With further knowledge it will be
possible to construct similar tables explanatory of the history of
the evolution of all characters of animals, so that the one now
given is only preliminary.

1 From the Proceedings of the American Association for the Advancement of Sct-
ence, for 1883.

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148 COPE. [Vot. III.

i) THE LIMES

The origin of the structures of the limbs of Mammalia will
be considered under four heads. zrs¢. The proportions of the
parts of the limbs. These, as is well known, vary exceedingly.
The diversity is readily perceived on comparison of the four
limbs of man, the horse, the whale, and the bat (Figs. 1-5—11-
24); and nowhere is the relation of structure to a function of
motion more obvious.

Second. The number of the digits. The Condylarthra have
five digits on both feet, and they are plantigrade. This character
is retained in their descendants of the lines of Anthropoidea,
Quadrumana, and Hyracoidea, also in the Bunotheria, Edentata,
and most of the Rodentia. In the Amblypoda and Proboscidia
the palm and heel are a little raised. In the Carnivora and Di-
plarthra the heel is raised, often very high, above the ground,
and the number of toes is diminished, as is well known, to two
in the Artiodactyla and one in the Perissodactyla.

Third. The fixed articulations. In the Condylarthra the
bones of the two series in the carpus and tarsus are opposite
each other, so as to form continuous and separate longitudinal
series of bones. This continues to be the case in the Hyra-
coidea and many of the Quadrumana, but in the anthropoid apes
and man, the first row is partly displaced outwards so as to alter-
nate with the second row, thus interrupting the series in the lon-
gitudinal direction, and forming a stronger structure than that
of the Condylarthra. In the Bunotherian, rodent, and edentate
series, the tarsus continues to be without alternation, as in the
Condylarthra, and it is generally identical in the Carnivora. In
the hoofed series proper, it undergoes change. In the Proboscidia
the carpus continues linear, while the tarsus alternates. In the
Amblypoda the tarsus alternates in another fashion, and the car-
pal bones are on the inner side linear, and on the outer side
alternating. The complete interlocking by universal alteration
of the two carpal series is only found in the Diplarthra. In the
highest forms of the Rodentia and Diplarthra, the fibula and
ulna become more or less coossified with the tibia and radius,
and their middle portions become attenuated or disappear.

Fourth. The ginglymoid articulations. These include the

Nox. 2:4] THE HARD PARTS OF THE MAMMALIA. 149

articulations which are flexed, extended, and rotated. Such are
especially subject to the laws of motion, and it is in them that
the effects of the latter are distinctly seen. As an example, the
ankle joint is in the primitive Condylarthra, a flat joint, or not
tongued or grooved. In most of the Carnivora, in a few Roden-
tia, and in all Diplarthra, it is deeply tongued and grooved, form-
ing a more perfect and stronger joint than in the other orders,
where the surfaces of the tibia and astragalus are flat, as in the
Condylarthra.

I. THE PROPORTIONS OF THE LIMBS AND OF THEIR
SEGMENTS.

The length of the legs of terrestrial Mammalia has increased
with the passage of time. The inferior types of Mammalia now
existing, as Marsupialia, Rodentia, Insectivora, Edentata, have
short legs, with a few cases of extreme specialization as ex-
ceptions, such as Kangaroos, Rabbits, and Jerboas (hind legs
only), the Dolichotis patachonica, the Rhynchocyonidze and the
Sloths. In the orders which stand at the summit of the series,
as the Diplarthra, Proboscidia, Carnivora, and Anthropomorpha,
the legs are much increased in length, and this is especially
marked in certain forms which stand in all respects at the
summit of their respective orders. Thus in Diplarthra, the
deer, antelope, and horse are distinguished for length of limb ;
in the Proboscidia, the elephant; in the Carnivora, the large
cats and hyenas; in the Anthropomorpha, the fore limbs are
long in all, the hind ones especially so in man.

The cause of this elongation is apparently use. It is the hind
legs that are elongated in a straight line in animals that walk on
them, as man; and both, in those that walk on both, as the
elephant. In animals that leap with the hind legs these are
still more elongated, and are folded when at rest, and rapidly
extended when in motion. In animals that climb with the fore
legs, these are elongated, as in the Anthropomorpha except
man. In those that climb with all fours, all are elongate, as in
the sloths. It must be remembered that these elongations are
the sum of increments added one to the other through long ages
of use in geologic time. The mechanical character of that use
has not been identical. It is of two principal kinds, viz. :

150 COPE. [Vo. III.

impact and longitudinal strain. These two forms of energy
move in directions opposite to each other; the one as compres-
sion in the direction of the length of the bone; the other, as a
stretching in the direction of the length of the
bone. Both processes alike appear to have stim-
ulated growth in the direction of the length of
the bone.

Figure 1.— A. Phenacodus primevus, fore and hind limbs; &. Homo sapiens,
fore and hind limbs.

No: 2. THE HARD PARTS OF THE MAMMALIA. 151

a. Increase of Length by Impact.

The increase in the length of the legs has not been always
due to increase in length of the same segment. In a majority
of the higher mammals, the increase has been principally in the
foot, and especially in the metapodials and digits, producing
digitigradism. In the forms which have remained plantigrade,
the femur (Proboscidia), or femur and tibia (Quadrumana), or
all three segments (Tarsius), have been the seat of the elonga-
tion. We can again trace these especial elongations to special
uses. In animals which leap, the distal segments of the limbs
are elongated; in those which do not leap, but which merely
run or walk, it is the proximal segments of the
limbs which are elongated.

Animals which run by leaping are divided into
those which run and leap with all fours, as Dip-
larthra ; and those which run and leap with the
posterior limbs only, as the jerboas and kan-
garoos. In both types, the
distal segments of the hind
limb are elongated, and in
the Diplarthra, those of
the fore limb also.

Animals which do not
leap in progression (ele-
phants, Quadrumana, bears)
are always plantigrade, and
have very short feet, but
elongate thighs, and most-
ly, tibias.

These? factsi’rendér it
highly probable that those
elements which receive the
principal impact in pro-
gression are those which
increase in length. In dig-

Figure 2.— Pes of (A) Merychocherus montanus ; (B) Bos taurus, much reduced.
Ca. Calcaneum; As. Astragalus; Ma. Navicular; Wcé. Naviculocuboid; Cz. JWec.,
Ecto-mesocuneiform; J/¢. Metatarsals (cannon bone); Zc, Entocuneiform.

152 COPE. [Vot. III.

itigrade animals it is the feet which receive the impact of the
repeated blows on the earth while in progression, while support-
ing the weight of the body at every stage of the process. In
plantigrade animals it is the soles of the feet and the bones
of the leg in line with them, which receive the impact, while
the feet beyond this point receive none, and do not support
the body except very partially at the moment of leaving the
earth. In the case of some of
the Quadrumana, the prehensile
use of the feet renders any con-
siderable impact impossible, so
the feet and hind leg generally
have remained short. But in the
case of the Tarsius, the habit
of leaping has been added to the
functions of arboreal progres-
sion, and the result has been
a remarkable elongation of the
posterior foot. But it has not
been the metapodials and digits
which have experienced this

Figure 3. — Tarsius spectrum, poste- elongation, since they have been
rior extremity, external side: from De always employed in prehension.
Blainville. It has been the tarsus proper,
the astragalus, and calcaneum, whose distal extremity is the
very point which in a plantigrade animal must receive the impact
of a leap under such circumstances.

In all of the above cases the impact is more or less directly
longitudinal, or in the direction of the length of the bone, at
some stage of the act of progression.

B. Increase of Length by Stretching.

Examples of this kind of stimulus to the elongation of bones
of the limbs are to be seen in those animals which are, for a
greater or less part of the time, suspended from the limbs of
trees. Such stretching must be, it is evident, in excess of mus-
cular resistance in the opposite direction, or an opposite effect
results. Thus the sloth hangs suspended from the limbs of trees,
exerting apparently no muscular effort in the act, maintaining

No. 2.] THE HARD PARTS OF THE MAMMALIA. 153

his hold by a curvature of the claws, which was in his ancestors
voluntary, but which has now become fixed by modifications of
the articulations themselves. This habit has resulted in a pro-
gressive lengthening of the bones of both the leg and the foot,
but especially of the leg, and most of the fore leg, which has
prehensile uses not experienced by the hind leg, in serving the

feeble intelligence

of the animal. RC ea othe
A similar case iF ih lane

ot velon sation

through _ suspen-

sion is that of the

fore les of the
Quadrumana. This
modification of
structure is direct-
ly as the habit of
swinging by the
fore leg, as in the
Ateles of South
America, and in
the Simiidz of the
Old World. Inthe
genus Hylobates
the habit of pro-
gressing rapidly
through the forest
by swinging from
they Horie legs,
reaches a maxi-
mum. The aban- Figure 4.—Tarsi of bats, much enlarged; from H,
donment of this atten. 4. Rhinolophus capensis. B. Carollia brevicauda,
habit by man has C. Chilonycteris sp. D. Rhynchomycteris sp. E. Ves-
resulted in the pro- pertilio subulatus. F. Atalapha noveboracensis. Letter-

ing: 4 tibia; f fibula; a. astragalus; ca. calcaneum; cal,
calcar; cw, cuboid; x, navicular; 7, 2, 3, tarsalia.

gressive — shorten-
ing of the fore limb,
both in comparison with the apes, and between the higher and
lower races.

In certain types the proportions of the tarsus have undergone
modifications from the same cause, In the sloths, the astragalus

154 COPE. [Vot. III.

and calcaneum are elongate. In the bats they are still more so,
and do not possess any distinct trochlea. The greater modifica-
tion of the tarsus in the bats is due to the fact that the order
Chiroptera dates from the lower Eocene epoch, while the arbo-
real sloths originated in the Pliocene; also, perhaps, because
they are suspended from the hind legs only, while the sloths
hang from all four. In the latter the carpus does not share
considerably in the elongation of the tarsus, but the phalan-
ges are greatly elongate. In the Chiroptera the heel of the
calcaneum is the line of attachment of a dermal membrane
through which it has experienced a continual lateral strain.
Concomitantly, it has grown to an enormous length. It is
not so easy to understand the mechanical law which ex-
plains the growth of a part through lateral strain as through
longitudinal strain, It is, however, not difficult to understand
why this very elongate heel should become segmented off from
the body of the calcaneum by the lateral strain of the caudal
membrane, as it has.

y. Modifications through Other Use and Disuse.

That the loss of articular condyles follows from a disuse of
the articulation may be readily shown. That a segment of a
limb may be shortened by a transfer of its function to some
other segment may be also demonstrated. That muscular in-
sertions have been enlarged or diminished directly as the use
of the muscles inserted in them, is apparent from the facts.

The enormously developed muscular insertions of the hume-
rus in mammals which dig are well known. Illustrations of this
are seen in the existing monotremes, Platypus and Tachyglossus,
the armadillos, and still more strikingly in the moles. Large
development of unequal phalanges is characteristic of all these
animals, but it reaches excessive proportions in the Cape ant-
eater Orycteropus, and in the giant armadillo. Huge develop-
ment of the muscular insertions of the humerus and of the
scapula are especially noticeable in animals which pull the vege-
tation on which they feed to them from elevated positions or
from below the earth, as in the extinct edentates of the fam-
ily Megatheriide. As the sloths grew smaller in dimensions,
the trees refused to yield to the diminished prehensile power of

No. 2. } THE HARD PARTS OF THE MAMMALIA. 155

the fore legs. The result has been that the sloths ascended the
trees, and their limbs assumed more and more the character of
mere suspensors of the weight of the body. Thus the muscular
insertions of the humerus diminished, and their humeri are to-
day furnished with weak ones only, the greater and lesser tuber-
osities of the head having nearly disappeared, so that the head
of the humerus resembles that of other arboreal mammals, as
the Quadrumana and Simiide.

The limbs have undergone great modifications of form in
their gradual adaptation to aquatic
habits. The stages of this process
are to be observed first in the sea-
otter (Enhydra), then in the seals,
then in the sirenians, and lastly
in the Cetacea. This succession
is not given here as a phylogeny,
for paleontology does not warrant
any such history.

The use of a limb as an oar for
propulsion in the water requires
that it shall be, so far as the blade
is, Concermed, inflexible, “Such a
structure has existed in all thor- /
oughly aquatic vertebrata. This
implies the immobility of the ar-
ticulations, which is due to the
loss of their condylar surfaces.
This may be traced to disuse of
such articulations. This disuse
would be at first voluntary, the
limb being held stiffly while used , cA te Bie eae
as an oar in thes acieos swim- hei ME PIORU Ce et
ming. Loss of power of extension
and flexion is well known to result from disuse. It is well known
that the flexors and extensors of the manus have become atro-
phied in the Cetacea. Not so, however, with the flexors and
extensors of the humerus, which become those of the entire
limb. In the whales the first segment of the fore limb is en-
closed within the integument of the body, so that its motion
being much restricted, the insertional crests are reduced in size.

156 COPE. [VoL. III.

In the eared seals (Otariidz) the hind limbs are somewhat free
from the body integument, so that they can be turned forward
when on land. They are further enclosed in the true seals
(Phocidz) so that their motion is very slight and they cannot
be used for progression on land, and are available only for
swimming.! It is supposed by Gray and Ryder that the solar
and digital parts of the posterior limbs of the seals are repre-
sented in the flukes of
the Getacea,;.)” hese
parts are supposed to
have separated from
the proximal parts of
the limbs, which have
been reduced in size;
and finally nearly atro-
phied through disuse.
This view is supported
by Ryder by consid- ~
erations derived from
studies in the embry-
ology and anatomy of
the Ceétacea,?’ with
much force. The phy-
logeny, however, re-
mains uncertain, owing
to our extremely de-
fective knowledge of
the extinct ancestors
of their order.

Figure 6.— Muscles of the posterior leg of Pu-
zorius vison, showing the position of the gluteus max- :
imus (Gma.) muscle; Ge, gluteus medius; #, rec- The earliest aPPprox-
tus; V, vastus. imation to the rela-

tions of the muscles and bones of the hind legs of the seals
is seen in the aquatic Mustelidz, as the otters and the mink.
In the latter (Putortus vison) the gluteus maximus muscle has
extended its insertion all the way to the distal extremity of the
tibia, thus flexing that segment, and gaining power in the stroke

1 On the Development of the Cetacea ; Report of Commissioner of Fisheries of U.
S., 1885 (1887), p. 445.

2 On the Eared Seals, Otartide, with Detailed Descriptions of the North Pacific
Species. By J, A. Allen. Aull. Mus. Compar. Zoblogy, Cambridge, I1., No. 1.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 157

of the foot against the water. This is followed by the suc-
cessive shortening of the femur, which from being a lever has
become a fulcrum for the tibia and hind foot. In this position,
where it is comparatively fixed, it undergoes successive abbre-
viation and thickening, until it assumes the form characteristic
of the seals (Figs. 6, 7).

Use and disuse play an important part in the determination
of the forms and proportions of the phalanges. In oar-like
limbs adapted to swimming, like the other segments, they lose
their condyles and become immovable on
each other, as in the Cetacea and Sirenia.
In the seals the flexibility of the digits is
greater, as their line of aquatic ancestors
is shorter. They add an especial pecul-
iarity in the superior size of the internal
digit of the fore foot, and of the internal

Figure 7.— Anterior and posterior legs of the seal A/onachus albiventer ; from

Cuvier.

and external digits of the hind foot. This must be ascribed
to the strains incident on use, and the consequent increased
nutrition of the parts. Seals constantly rest on shore and on ice-
floes, in a manner unknown to both Sirenia and Cetacea. The in-

158 COPE. [Vot. IIT.

ternal digit of the manus is necessarily the support of the body
when in the act of climbing out of the water and is used in such
progress as they make when on the shore. The hind feet are
used in the same way ; but I must note here, that I do not know
to what use the external digit is put which shall account for its
superior development. Observation on the living animal only
ean furnish the explanation.

In the heavy Ungulata the longitudinal diameter of the
phalanges is greatly reduced in relation to their transverse.
The successive increase in depression in the bones of the feet
with the advance of time is to be most readily seen in the order
Amblypoda, where we pass from Pantolambda to Coryphodon
and Uintatherium (Fig. 8). A similar successive reduction is
to be seen in the lines of the Perrisodactyla, as we om (ii
pass from the smaller and lighter to the heavier and
more bulky types. Such series are those which com-
mence in the Lophiodontidz, and terminate in the
Menodontidz on the one hand, and the rhinoceroses
on the other. The elephants display the end of a
similar line, which
commences in the
Condylarthra. In
all of these bulky
mammals the
weight in progres-
sion is borne on

Hi

iw

(i

Figure 8.—a, Pantolambda bathmodon, digit of posterior foot. 4, Right posterior
foot of a species of Coryphodon from New Mexico, one-half nat. size. From Report
Expl. W. of tooth Mer., G. M. Wheeler, IV., Pl. LIX. c, Uintatherium mirabile,
right posterior foot; from Marsh, Dinocerata,

No. 2.] THE HARD PARTS OF THE MAMMALIA. 159

the extremities of the metapodial bones, and the phalanges take
but little share in it. They are turned forwards and are nearly
useless. Their great reduction in dimensions in these forms
appears to me to have followed disuse, and this is then the
probable cause of it.

2. THe NuMBER OF THE DIGITs.

The reduction in the number of toes is supposed to be due to
the elongation of those which receive the greater number of
strains and impacts in rapid progression, and the complementary
loss of material available for the growth of those not subject to
this stimulus. This is rendered probable
from the fact that the types with reduced
digits are dwellers on dry land, and those
that have more numerous digits are inhabit-
..\ ants of swamps and mud, or are more or less
\ aquatic. That this inequality is due to these

: mechanical causes is still further indicated by
\ 4 the fact that in those forms where the soles
$ are thickly padded (Carnivora, Proboscidia)
the reduction has either not taken place, or
has made little progress, amounting to the
loss of only one digit. (An ap-
parent exception in the case of
the camels will be mentioned

Figure 9.— Anterior feet of primitive Ungulata, reduced. A, Phenacodus pri-
mavus. B, Coryphodon elephantopus. C, Hyracotherium venticolum.

160 COPE. OWAoren IK

later.) A still more important body of evidence which shows
that the inequality in size and number of digits is due to im-
pacts and strains unequally distributed, has been brought for-
ward by Ryder. He points out that definite results are to be
observed in those limbs of a given type of animal which expe-

Figure 10.— A, Right posterior foot of Protohippus sejunctus Cope, from Colo-
rado, about one-half nat. size. From U. S. Geol. Surv. Terrs., F. V. Hayden, IV.
B, Right posterior foot of Potbrotherium labiatum Cope, from Colorado, three-fifths
nat. size. From Hayden’s Report, IV., Pl. CXV.

rience correspondingly definite influences ; while in the limbs
where the strains are equal, the modifications do not appear.
Examples of this kind are to be found in the unguiculate Mam-
malia, and in the Marsupialia. Thus in the jerboas which use
the hind limbs in leaping, these only display reduced digits, the

No.2.] THE HARD PARTS OF THE MAMMALIA. 161

fore limbs remaining of primitive character. The same is true
of the kangaroos. In digging genera the fore limbs experience
the modifications, while the hind limbs are more normal, as in
Chrysochloris and various Edentata.

Ryder sums up the evidence in two propositions as fol-
lows : 1—

“JT. The mechanical force used in locomotion during the
struggle for existence has determined the digits which are now
performing the pedal function
in such groups as have under-
gone digital reduction.

“TI. When the distribution
of mechanical strains has been
alike upon all the digits of the
manus or of the pes, or both,
they have remained in a state
of approximate uniformity of
development.”

The application of the im-
pact, or strain, or both, in pro-
gression, is easily understood.
In recover (see p. 166), the leg
is bent on the foot as it rests
on the ground, and those dig-
its which then leave the
ground last, sustain greater
strain than those which leave
it sooner. In replacing the
foot ,on the ground (planta-
tion), those digits which strike Figure 11. — Equus caballus, fore and
it first, experience greater force ping feet; from Cuvier.
of impact than those which
strike it later. Supposing the five primitive digits to have been
of equal length, the distribution of the impact and of the strain
will depend on the angle at which the foot is directed with
reference to the direction of motion. If the feet are pointed
forwards, the middle digits will experience strain and impact ;
if outwards, the inner digits bear the weight; if inwards, the
external digits receive it.

1 American Naturalist, 1877 (Oct.), p. 607.

162 COPE. [Vot. ITI.

Observation on five-toed plantigrade Mammals shows that their
feet are turned neither inwards nor outwards in progression,
but straight forwards. It is probable that the primitive Mam-
malia moved in the same manner. This is also to be inferred
from the fact that they were plantigrade, so that the leverage
transversely in or out which results from the elevated heel
of the digitigrade leg was wanting to them. In progression
of this type the middle digits of course leave the ground last,
and strike it first. Thus the middle toes have been stimulated
at the expense of the lateral ones, so that in the Diplarthra,
either the middle one (Perissodactyla) alone remains, or the
middle two (Artiodactyla). In the kangaroos, the external
toes have been chiefly used, so that the fourth and fifth digits
have been principally developed. In man, who now turns his
feet out when using them as bases of resistance to muscular
labor, the inner digit has become most robust. The mechanical
history of the human great toe is however yet unknown.

As regards the equal development of the third and fourth
digits in the Artiodactyla, as distinguished from the develop-
ment of the middle digit of the Perissodactyla, I have advanced
the following hypothesis. I have supposed that the primitive
members of this former division sprung from pentadactyl plan-
tigrades who dwelt in swamps and walked on very soft ground.
The effect of progression in mud is to spread the toes equally
in all directions and on each side of the median line. Such feet
remain in the mud-loving hippopotamus, and to a lesser degree
in the true pigs. From such ancestry the cloven-footed Diplar-
thra derived their characters. The Hyracotheriine, the ances-
tors of all Perissodactyla, display on the other hand evidence
of a life on harder ground, especially in the posterior foot, where
articulations are already rigidly defined, and the third digit is
longer than the others. Some of their descendants love
swamps, as one or two species of tapirs and rhinoceroses, but
others live on the dryest ground, as the Andean tapir, and
the African rhinoceros. As to the highest members of both
even and odd toed groups, the Bovide and the Equide, their
habitat is in the vast majority of cases the dry land (Fig. 12).

Continued and excessive prehensile strain with weight on
the longest digits, must be assigned as the cause of the espe-
cial elongation; and disuse as the cause of the loss of the

No. 2.] THE HARD PARTS OF THE MAMMALIA. 163

external and shorter digits, of the sloths; so that there remain
but two and three (Choloepus and Bradypus), and in the climbing
anteater (Cycloturus) but one principal toe, and two rudiments.

Figure 12.— Manus of Artiodactyla, much reduced; from Kowalevsky. 1, //7zp-
popotamus ; 2, Hyopotamus ; 3, Sus; 4, Gelocus,; 5, Cervus.

The excessive strain and impact experienced by certain digits in
leaping, accounts for the digital reduction in the hinder foot
of the kangaroos and jerboas, precisely as in the Perissodactyle
ungulates.

3. THE Fixep ARTICULATIONS.

On entering the subject of the articulations, a preliminary
observation on their origin must be made. No evolutionist can
doubt that the discontinuity of matter, expressed by an articula-
tion, is due to flexure of the body exhibiting it. Primitively, the
softer tissues of which all animals were composed, as the inferior
forms are to-day, were susceptible of flexure in various direc-
tions. The deposit of hard mineral or organic substances
within the tissues, producing calcareous layers, chitin, horn, and
bone, has not in a majority of cases suppressed motion, but has
restricted it to definite directions. It cannot have been other-
wise than that, since the motions of animals continued during
the evolution of their hard parts, these hard parts grew in exact
adaptation to these movements. Thus at the points of greatest
flexure joints would be formed, and between these joints the
deposit would be continuous.

164 COPE. [Vot. III.

The fixed articulations are not absolutely without movement,
because termed fixed. When two adjacent bones become entirely
motionless through the fixity of their positions, they are apt to
coossify, especially if growth be stimulated by impact of the
parts. Such a case is the confluence of the cuboid and navicu-
lar bones in the Bovidee and Equide, and the fusion of the cunei-
forms in some of the former. Such are the fusion of the mag-
num and unciform in the manus of the Cycloturus, and of the
trapezoides and magnum in Bradypus. Such the union of the
metapodials in both extremities of the three-toed sloth. The
fusion of the scaphoid and lunar bones in the Carnivora is not so
readily explained. It may be, however, traced toa strain similar
to that experienced by the feet of sloths, Cycloturus, etc., but for
a different purpose, that of seizing and rending prey. But this
suggestion may be worthless, and it does not offer any demon-
stration as to how such strains should produce such result.

The fixed articulations are those between the carpal and tarsal
bones, and those between these and the metapodials. In the
Diplarthra another fixed articulation is that between the ulna
and radius, and in this and other orders, that between the tibia
and fibula.

a. The Ulna and Radius.

The relation of the head of the radius to the ulna is, in lower
land vertebrates, a more or less loose one. In the lower Mam-
malia the head is generally oval, permitting of greater or less
supination of the manus. In the higher Edentata and Taxeo-
poda, the head becomes round, permitting perfect supination in
the great anteater, the monkeys, and man. In the Ungulata its
development is in the opposite direction or towards fixity. It
becomes flatter, and incapable of movement ; and, finally, in the
Artiodactyla, it is firmly articulated with the ulna by a coarse
peg and notch, or gomphosis, followed by coossification in the
Camelidz. It is evident that the rotundity of the bead of the
radius has been produced by the more or less successful attempt
to’ rotate it in the act of supinating the manus. The immovable
condition seen in the Ungulata is as clearly due to disuse of the
supinating function, in a use of the fore limb where such move-
ment is unnecessary. It appears that the impact or concussion
of the blow of the ungulate foot on the ground has caused an

No.2.] THE HARD PARTS OF THE MAMMALIA. 165

expansion of the external border of the head of the radius over
the adjacent external part of the ulna. The latter forms, in the
Diplarthra, a more or less evident ridge, corresponding with the
external condyle of the humerus, while the internal border forms
another ridge, which corresponds to the internal condyle of the
humerus. These elevations are due to the existence of greater
friction, z.¢. stimulation, in front of convex condyles than is pos-
sible at the point of the cotylus which receives the groove of
the condyles. A groove of the coronoid surface of the ulna,
opposite the groove of the condyles, exists accordingly in most
ungulates, since here contact, friction, and impact are at a mini-
mum. The head of the radius fits this groove, which is at first
quite shallow, as in the peccary and hog. In the extension of the
head of the radius externally, the latter naturally embraces the
external ridge of the coronoid surface of the ulna. This embrace,
together with the opposite descent of the head of the radius into
the median groove, constitute a very strong double open peg
and notch, or short tongue and groove, articulation. This is
most pronounced in the highest Diplarthra, as the crests of the
ulna tend to become more elevated under the influence of the
impacts and friction conveyed to them through the convex parts
of the humeral condyles. This articulation, like all those of the
Diplarthra, is a protection against dislocation from lateral strains
and blows. For an explanation of the origin of the elbow joint,
see page 179 (Plate I.).

B. The Carpus and Tarsus.

The conversion of a taxeopod into a diplarthrous ungulate
has been accomplished by the rotation outwards of the lower
leg with the first row of the carpus and tarsus, on the second
row ; or else by the rotation inwards of the second row on the
first, in both the fore and hind feet. The question to be solved
here is, which row has moved from its primitive relation, or in
what direction has the energy of rotation been applied. After
long and careful observation of the locomotion of living Mam-
malia, and especially Diplarthra, I have reached the following
definite conclusions : —

In locomotion each foot occupies two relations to the act.
The first is the setting-down of the foot, or plantation; the
other is the lifting of the foot from the ground, or vecovery, to

166 COPE. (Vo. III.

use the nomenclature of Dr. H. Allen. In plantation, planti-
grade mammals do not turn the toes outwards ; while digitigrade
forms do turn them out. This may be readily observed in

anterior and pos-

Poe terior views of
most of the Dip-
x ‘- larthra in motion,

and especially in
Artiodactyla. In
plantation, the el-
bows and hocks
rotate inwards, and
the toes outwards.
In recovery, this
rotation is neces-
sarily continued.
As the body pass-
es the position of
the stationary limb
and foot, it gives to
the latter a slight
twist outwards and
forwards, in answer
to which the foot
is lifted from the
ground, or recov-
C ered. At recov-

Figure 13.— Procyon lotor, gaits; from Muybridge, €Ty, the rotation
Animal Motion. 4 shows semisupination of the left ¢c@yznot be in any

manus and lever strain on right pes in recovery; 4, lever other direction in

any mammal; in
plantation, it say
de forwards and inwards, or forwards and outwards. In recov-
ery, the twist is greater in a long than in a short limb. In
the language of mechanics, the length of the arc of torsion
is directly as the length of the limb. It is probable that it is
for this reason that the digitigrade forms turn the toes out in
plantation also, the structure having adapted itself to this mo-
tion, so as to perform antero-external rotation most easily.’ In

strain on recovery of right manus, and plantation of left
pes; C, plantation of left manus.

1] have made these observations on various species of Auchenia, Camelus, An-
tilocapra, Antilope, Capra, Bos and Cervus, and in Tapirus, Rhinocerus and Equus,

167

THE HARD PARTS OF THE MAMMALIA.

Te

Ligure 14.— Casella dorcas, gazelle; from the Standard Natural History.

168 COPE. [Vov. III.

plantation, the rotation of the foot is arrested at the moment of
contact with the ground, with the result of producing a torsion
of the segments of the limb on each other. The energy of the

torsion is directly as
the distance from the
moving body, since
its cause resides in the
inertia ‘af ithe fvec
hoof, which is that of
the animal of which it
is a part.

The mechanical ef-
fect of this torsion is
seen at various points
on the length of the
lim Dy «sin. the store
limb (I.) the distal ex-
tremity of the radius
has spread outwards so
as to cover almost the
entire carpal articula-
tion, and the ulna has
been excluded from it.
That torsion with im-
pacts, the’ Cornect
explanation of this
divergence from the
condition of lower land
vertebrates is rendered
probable by the large
ulnar carpal articula-
tion in primitive plan-
tigrade types with
taxeopodous carpus, as

Figure igp — Boicharus humerosus, Cope; distal Elephas, Hyrax, and
extremity of radius, showing oblique intercarpal keels; Ph d IL Th
do. of humerus; also left fore foot from front and : enacoaus. : e€
from inside; one-fifth nat. size. lines of mutual contact

in the zodlogical garden of Philadelphia. The horse turns the toes out but little, and
frequently turns them in; but the tapir, which represents the horse’s ancestors, turns
them out. The llama also turns the hind toes out very little, or not at all.

‘Nor 2: ] THE HARD PARTS OF THE MAMMALIA. 169

of the carpal bones of the
first row have become ob-
lique, outwards and for-
wards, in the Artiodactyla,
except the Camelidz ; and
Hemee the intercarpal
crests of the radius have
become oblique in the
same way. III. The bones
of the first carpal row have
come to occupy the posi-
tions above the lines of
separation between those
of the second row, thus
producing diplarthrism.

IV. The bones of the first carpal row have
‘moved to a position external to the axial lines
of their corresponding digits (e.g. the lunar
is external to the axis of the third metapodial

in Perissodacty-
la (Fig. 16) and
Artiodactyla
(Figs. 12-15),
instead of above
it as in Taxeo-
poda (Fig. 16).

C

Figure 16, — Manus of Phenacodus (4) and Perissodactyla; viz. :

B. Hyracothe-

rium venticolum, C. Hyrachyus agrestis; D. Rhinocerus unicornis; E. Equus
caballus ; all showing external transposition of os dunare, L. P. Line of strain in

plantation; R. Do. in recover.

wr \

170 COPE. [Vot. III.

In the hind leg similar phenomena are exhibited. I. The
fibula has been almost entirely excluded from the tibio-tarsal
articulation. II. In some forms (the equine line) the tibio-
astragalar tongue-and-groove joint has become oblique outwards
and forwards. III. The astragalus (of the first tarsal row) has
extended its distal articular surface on the cuboid (of the second
row), so as to exclude more and more the calcaneum.

That these changes, so remarkably similar in all of the artic-
ulations of the legs, have resulted from the torsion in question,
is rendered highly probable by the fact that they have appeared
in all lines of descent, except that of the Amblypoda, in direct
ratio to the advance of digitigradism in the Ungulata, and the
measure of the one is a measure of the other.

The movement involved in the preceding discussion is that of
plantation. In recovery, we meet with another element in the
problem. In spite of the outward rotation of the bones of the
first carpal and tarsal rows, the bones of the second row have
not moved outwards on the metapodials. They have remained
stationary as regards the axis of support, while the me¢apodtals
have been evidently pressed outwards. This is seen in two
points. First, the external bone of the second row, the uncl-
form, is in all Diplarthra much extended inwards. It reaches
contact with the middle bone of the first row (the lunar) before
the internal bone of the first row, the scaphoid, has extended
outwards beyond the trapezoides to the magnum. This is the
permanent state of affairs in the Amblypoda (Fig. 9). Second,
the metapodial bones abut with the external sides of their
proximal extremities against inner distal facets of the second
row of tarsals. This must have been brought about by an
inward movement of the second row of tarsal bones, or by an
outward movement of the metapodials to meet them. The
direct effect of the arrest of outward torsion of the foot is to
‘dislocate the tarso-metatarsal and carpo-metacarpal articulations,
unless some antagonistic movement prevent it.

A strain antagonistic to the external movement of the tarsal
bones is introduced at the moment of recover of the foot. Dr.
H. Allen shows in his exposition of the Muybridge photographs,
that in approaching the recover, the weight supported by the
foot is transferred to its inner border, a movement which nec-
essarily throws the strain on the external sides of the heads of

No. 2.] THE HARD PARTS OF THE MAMMALIA. 17I

the metapodials. Hence the apparent outward movement of
the latter. The structure, however, represents an inward pres-
sure of the second row of carpal and tarsal bones on them. The
bones of the second row are then subject in locomotion to two
influences which tend to shift them from their position. First,
the pressure outwards on plantation, derived from the weight
borne by the leg, and resisted by the metapodials on the ground;
and second, pressure inwards of the weight, on its transfer to
the inner side of the foot, also resisted by the metapodials on
the ground on recovery. The weight is the same in both cases,
and there is no reason to doubt the equal velocity of the two
strains. Hence the effect of the one is neutralized by the
other, and the bones of the second row retain their position.!
It is obvious that in the beginning of the rotation of the first
on the second row of carpals and tarsals, of a taxeopodous
mammal (Fig. 16), the inferior bounding angles of the former
would be arrested by the superior bounding angles of the latter,
especially if there should be any play of longitudinal motion of
the digits and carpal and tarsal bones resting on them. Such
play there would be in a taxeopodous foot. This arrest would
flatten the opposing angles and produce planes or facets, and
diplarthrism would have its beginning. The angles separating
these planes would penetrate deeper into the fissures separating
the bones under the influence of concussions. (See carpus of
Boéchoerus, Fig. 15.) In some instances, as in the Oreodon-
tide, some Tragulidz, and Elotherium, the lunar has pene-
trated so far as to almost divide the second row of carpals.
An important result of the outward movement of the bones
of the first carpal and tarsal rows has been to leave unsupported
the internal element of the second row, the trapezium and the
entocuneiform. As a consequence of this, these elements come
to have a mere lateral attachment, which is not favorable to the
rigidity of the pollex and hallux which are attached to them.
This condition leads to disuse, which the strain of the inner
side of the foot in recover is@not sufficient to overcome. The
external digit of each foot, on the contrary, remains, since its

1Jn my original discussion of diplarthrism (American Naturalist, Dec., 1888),
I omitted to consider the history of the second row of carpals and tarsals. This de-
ficiency is now supplied. I have been guided to the explanation by Dr. H. Allen’s
obseryations on p. 50 of his exposition of the Muybridge photographs,

17

COPE.

AN ANY,

(Vou. III.

PAs

~x
x

SOQe OES

OS

fo)

Figure 17.— Smilodon neogeus Lund, from the Pampean formation of Buenos Ayres: after Burmeister.

Ne@: 2.1] THE HARD PARTS OF THE MAMMALIA. 173

connection with the carpus and tarsus is maintained. In the
developed taxeopodous posterior foot, on the contrary, the hallux
remains for a much longer time, as in Carnivora; and where it
has been especially used in prehension, as in Quadrumana, it
becomes enlarged. In man it receives especial strain in recover,
particularly in those men who turn out the feet in walking. To
this cause we may ascribe the gradual increase in size of this
digit, until in the highest races it exceeds the second digit in
length.

The above reasoning when applied to the Unguiculate series
is modified by the existence of other conditions. In the Carni-
vora the weight of the body does not rest on the ungues as in
the Ungulata, but on the pads of connective tissue beneath
the digits. Consequently, on the application of the foot to the
ground, the distal bones in the carpal and tarsal articulations do
not present the rigid resistance seen in the Ungulata, but yield
more or less to the torsion. Hence, no alternation of these bones
takes place in the hind foot of the Carnivora, where the ever-
sion of the digits is moderate. In the case of the fore foot, the
eversion and consequent torsion are so much greater, that the
alternation is produced (Figs. 17, 18). In the plantigrade bear
the alternation is almost nil. |

It may be here objected that the camel walks upon elastic
pads as do the Carnivora, and yet the alternation has really taken
place. It is on this account (as I have maintained) that the dis-
tal metapodial tongue keels were never completed in these
animals. But if the camel does not rest on the ungues with
sufficient fixity to resist torsion, thus resembling in some degree
the Carnivora, the ancestors of the camels, the Poébrotheriide,
resembled other Diplarthra in this respect. As already pointed
out, their foot structures were like that of other Artiodactyla, the
palmar and solar pads of their descendants are of comparatively
modern origin. Their diplarthrous structure is inherited.

The carpus of the Anthropomorpha and Quadrumana present
some interesting modifications. In most of the genera the
arrangement is taxeopodous, but in the Simiidz the scaphoides
extends somewhat outwards over the magnum, and the lunar com-
pletely overlaps the cuneiform (Fig. 19). In man (Fig. 2) the
lunar extends externally over the cuneiform, and the scaphoides
rests partly on the magnum, giving an arrangement similar to

COPE. (Vor. III.

Figure 18. — Hyena striata, striped hyena, showing position of feet; from the
Standard Natural History.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 175

that of the Diplarthra, but of inferior fixity. In the baboons
(Cynocephalus) the relations of the lunar and unciform are as
in man, while the scaphoides through the centrale, which has a
strong lateral facet for the magnum, rests entirely on the trape-
zoides, thus approximating the arrangement in the Amblypoda.
In Anthropomorpha the metacarpals are nearly in line with the
carpals of the second row, inclining, however, to articulate in
addition with the carpal to the zzmer side of them, contrary to
the arrangement in other Mammalia. This disposition is little
marked, however, being restricted mainly to the fourth meta-
carpal, which has more or less contact with the os magnum.

The relation of the form of the bones of the manus to their
uses is obvious in this order. The Simiidz use the fore limb as
a suspensor, as they swing from branch to branch of the forests
in which they live. The swing of the body on the arm is
divided into two parts, in which the strains are opposites of each
other, as to the metacarpal, but identical as to the cubito-carpal
articulations. The change of relation to the point of suspen-
sion when swinging from one place to another, is permitted by
the rotation of the manus and radius round their long axis, so
that an act of supination is performed. The strain on the
proximal carpal bones by the radius is then outwards, which
accounts for the external extension of the scaphoides over the
magnum. The lunar also is carried by the same strain far
external to its usual position, entirely covering the cuneiform.
The latter and the unciform are small, and the cuneiform is
comparatively unimportant. This restriction of the two ele-
ments of the external row of the carpus is to be accounted for
on the ground of disuse. The weight is principally supported
by the scaphoides and lunar, and the strain passes exclusively
through them as they only are grasped by the fore arm, z.e. by
the radius. The ulna has either very slight or no contact with
the cuneiform, serving merely as the point of suspension round
which the radius and hand rotate. The relation of the fore-arm
to progression is quite the reverse of that seen in the Ungu-
lata, where it sustains so much impact and strain. The meta-
carpo-carpal articulation is not modified. In approaching the
position below the point of suspension, the strain of the weight
is outwards from the fixed point. This presses the heads of the
metacarpals inwards on the carpus, and the segments proximal

176 COPE. [Vor. IIT.
to the former, outwards on each other. Beyond the point of
vertical suspension the strain on the heads of the metacarpals
presses them outwards, thus antagonizing the effect of the in-
ward pressure. The linear relation therefore remains unaltered,

SO GTI a

Figure 19. — Simia nigra, carpus one-fourth the nat. size.
Figure 20.— Bradypus tridactylus, carpus one-fourth nat. size.

In the sloth (Aradypus tridactylus), which also progresses in
suspension, the rotation of the radius and manus is far less
considerable than in Simia; is in fact almost wanting. In pro-
gression the strains are alternately opposite each other at the
cubito-carpal articulation, and as a consequence the scaphoid and
cuneiform are subequally developed and at the expense of the
distal part of the lunar. The equality of these opposed strains
is also represented by the similarity of the articular surfaces
between the scaphoid and trapezoido-magnum, and the cunei-
form and unciform (Fig. 20).

I can offer no plausible theory to account for the diplarthry
of the human carpus. The movements of the human hand are
so many and various that the explanation of its carpal structure
is a most complex proposition (Fig. 1 B, p. 150).

An especial peculiarity characterizes the cubito-carpal and
intercarpal articulations of the Anthropomorpha, Quadrumana,
and sloths. Both of these articulations are strongly convex
proximally, offering halves of ball and socket joints. In the
intercarpal articulation the articular surface covers a large ante-
rior face of the magnum and unciform bones. This form is
represented by a trace only in Ungulates. Its function evi-

No. 2.] THE HARD PARTS OF THE MAMMALY/A. 177

dently is the inward flexion of the manus, and it is especially
characteristic of forms which suspend themselves by the fore
limbs, as above pointed out. It is not difficult to perceive in
this instance how the function has produced the structure by
use. Continued flexion and extension has rounded the angles,
especially on the dorsal side of the carpus, and the stimulation
has elongated the elements in the direction of greatest pulling
strain; z.e. longitudinally (Fig. 20). This is in great contrast
to the flatness, both transversely and anteroposteriorly, seen in
Artiodactyla and horses, where the parts have been subjected to
impact from hard earth for so long a period.

Some apparent exceptions to the above general principles
must be now referred to. The genera Hyrax and Dendrohyrax
are closely allied, yet the one displays a taxeopod, and the latter
a diplarthrous tarsal structure (Osborn). A preparation for the
latter is seen in some Periptychidz, and in some Carnivora, as
Ursus and Mustelidz, in the extent of the contact of the condyle
of the head of the astragalus with the cuboid, without the produc-
tion of a facet on either. This facet could be, however, easily
produced by the simple flattening of the appressed surface by
impacts, and this is, it may be supposed, what has taken place
in Dendrohyrax. Observations on the movements of the spe-
cies of this genus in life are necessary to solve this question.

The Amblypoda of the Wasatch and Bridger epochs are dis-
tinguished by the great diplarthrism of the tarsus, although
they are plantigrade and pentadactyle (Figs. 8-10). In this order,
as already indicated, the feet have shortened with the advance
of time; and though it is hardly probable that they have
descended from a digitigrade type, their ancestor, Pantolambda,
was much more capable of varied movements than they. The
history of this line must be better known before any reasonable
explanation of the character of the hind foot can be reached.

4. THE GINGLYMOID ARTICULATIONS.

The mobility of the ginglymoid articulation depends on its
combination of convex with concave surfaces, which permit
flexion and extension of one bone on another; in other words,
they consist of a condyle and an adapted cotylus. The fixed
articulations consist, on the other hand, of adapted faces, which

178 COPE. [Vou. III.

do not admit of flexion and extension of the elements thus con-
nected. A transition from a ginglymoid to a fixed articulation
is seen in the modification of a Condylarthrous convex distal
articular surface of the astragalus into the fixed or facetted
distal articular surface of the Perissodactyla (Figs. 21-22c).
Another modification of the Condylar- :
throus astragalar surface is that seen in
the Artiodactyla. Here the mobility
continues, but it is divided into two con-
dylar faces which necessarily permit
motion in one direction only. It ap-
pears easy to account for the modifica-
tions of the Condylarthrous astragalus
into that of the two orders mentioned,
by supposing that it has
been due to long-continued
impacts applied at right
angles to the surfaces con-
cerned ; that is, with the
length of the foot. Ina
plantigrade animal such
impact is either transverse
or oblique to the length of
the foot, and as digitigrad-
ism progresses, the direc-
tion of impact is more and
more in the long axis. In

Fic. 22.

Figure 21. — Phenacodus primevus, carpus and tarsus; @, carpus, proximal view,
first row; 4, do. second row; ¢, tarsus, distal view of astragalus and calcaneum; @, prox-
imal view of second row of tarsals.

Figure 22.— Hyracotherium venticolum, posterior foot: a, left side; 4, front;
¢, distal view of astragalus and calcaneum.

Mammalia with soft pads on the feet, this chance does not oc-
cur; as Carnivora, Proboscidia, etc.

The movable or ginglymoid joints of the limbs are either sim-
ple or trochlear. The former are the proximal extremities of the
humerus and femur, and the distal extremity of the astragalus
in all except Diplarthra. The trochlear are enumerated further
on. That they all originated from the simple ginglymi is shown

No. 2.] THE HARD PARTS OF THE MAMMALIA. 179

by paleontology. The elbow joint passes from simple to troch-
lear, from the lower or less specialized Mammalia to the most
specialized. Nowhere is the direct mechanical effect of motion
more demonstrably evident than in the movable articulations of
the skeleton of the Mammalia.

a. Lhe heads of the humerus and femur represent smaller and
larger segments of spheroids, and both look in part upwards.
These articulations are not due to impact, but to rotary move-
ment of the movable limb element on the fixed scapular and
pelvic arches. This movement antedates in time the existence
of impact, since it characterizes the movements of aquatic ani-
mals which preceded the terrestrial. Neither of these articula-
tions acquired their spheroidal form until the advent of the
Mammalia. To the more constant and uniform activity of the
Mammalia, as compared with their reptilian ancestry, must we
ascribe the gradual rounding of the humeral and femoral heads,
which form the most nearly universal joints in their skeleton.

b. The Elbow Font. In lower salamanders, as Crypto-
branchus, the ulna and radius rest normally, like the tibia and
fibula, in the transverse plane of the distal extremity of the
humerus. In terrestrial Batrachia and Reptilia (Theromora,
Lacertilia), the plane of the ulna and radius is either oblique
or at right angles to that of the distal extremity of the humerus.
Mammalia possess the same character, the radius resting proxi-
mally above or anterior to the ulna, instead of alongside of it as
in the lower Batrachia. This position may be ascribed, I think,
to the long-continued action of the supinator muscles of the fore-
arm, together with that of the biceps flexor, in the endeavor to
use the fore feet for purposes other than mere locomotion.
Supination and flexion of the fore arm are necessary for any
use of the manus in connection with the head, or in order to
grasp any object which should project in front of it. In both
reptiles and mammals the condyle of the humerus is divided by
a shallow vertical groove ; that is, a groove in the line of the long
axis of the leg. This groove is due to the fact that when the
ulna and radius assume a relation transverse to the end of the
humerus, their transverse diameter, especially that of the ulna,
is less than the latter. The groove or median concavity is then
nothing more than the result of the pressure and impact of the
narrower ulna on the middle of the condyle, experienced during

180 COPE. [Vot. III.

active use. It results, also, in the lower Mammalia that the hu-
meral condyles project beyond the ulna and radius on each side.
The torsion experienced by the limb at the moment of contact of
the foot with the ground, produces a pressure of the inner end of
the condyle forwards and outwards against the corresponding part
of the ulna, and radius if it extend so far inwards. The external
part of the humeral condyle is correspondingly pressed back-
wards. The result is a flare of the inner anterior and posterior
external edges of both the condyle and cotylus, if there be any
free margin to either. Hence the obliquity of the ulnar cotylus
in Mammalia, whose locomotion is on the ground. Those
which, like the Anthropoid apes, swing themselves from branch
to branch of trees, experience alternate torsions of the fore leg
in both directions. Hence the edges of the ulnar cotylus are
flared equally in both directions precisely as the strain on the
material requires (Plate I. Fig. B). To this torsion we can as-
cribe also the development of a flange on the inner anterior edge
of the humeral condyle, in Condylarthra and Unguiculata in gen-
eral, and the corresponding oblique truncation of the adjacent
edge of the head of the radius, and the posterior flange of the
cotylus of the ulna on the external side. The humerus forms no
flange on the external side, because it does not overhang the ulna
sufficiently ; the ulna being itself the external bone of the fore
arm. Where the humerus does not overhang the inner side, as
in Hyrax, there is no flange of the former, and no truncation
of the head of the radius on the inner edge (Plate I. Fig. E).

In the lines of the Unguiculates, of the Edentates, and of the
Taxeopoda, there is an additional development of the power of
the supination of the manus. This is accomplished by the rota-
tion of the distal and of the radius round that of the ulna, and
the rotation of the head of the radius on its own axis. So the
head of the radius becomes more and more round, in consequence
of the mechanical constriction of its long axis, till in the great
anteater, the sloth, and the monkeys, it is perfectly round, and
rotates in its ligamentous ring, while maintaining its position on
the front of the ulna. In both of these types it lies on the
external side of the middle line, owing to the habit of supination,
which throws the radius more and more outwards. Perhaps it
is for this reason also that the ulna extends inwards proximally,
so as to permit of no internal humeral flange in both forms.

No. 2.] THE HARD PARTS OF THE MAMMALTA. 181

The notch between the head of the radius and the coronoid
process of the ulna is fitted by a corresponding ridge of the
humeral condyle, the intertrochlear crest, in the Anthropomor-
pha. In the Myrmecophagide it is wanting, because the me-
dian convexity of the ulnar cotylus is opposite the space between
the head of the radius and the coronoid process, so that the ulnar
concavity of the humeral condyle is immediately continuous with
the radial surface of the same.

In the elbow joint of the Diplarthra a different state of affairs
exists. The head of the radius lies firmly on the coronoid pro-
cess of the ulna, having the transverse diameter increased. This
increase of width I suppose to be caused by the strong impact
of the condyles of the humerus directly upon its extremity, which
accompanies the use of the limb as a support, especially in alight-
ing upon it in the rapid locomotion characteristic of diplarthrous
Ungulata. The increase in diameter is both external and inter-
nal, and so far as to equal the width of the humerus, and not
to permit any flange on the edge of its internal condyle. The
effect of impact on the head of the radius is greater than it is
on the condyles of the humerus, because its energy is expended
in the case of the former on a surface whose arc is only one-
third that of the latter. It must be remembered, however, that
it is not equally distributed on the humeral are. The coronoid
process of the ulna also expands transversely, but not to the
same extent as the head of the radius. Its external expansion
is overpassed by that of the radius, the external portion of the
radius in the Diplarthra occupying the position of the entire
head of that of man. The effect of the two convexities of the
humeral condyles has ‘been in most Mammalia to prolong in the
direction of their movement the corresponding parts of the coro-
noid region of the ulna. Hence there has appeared an external
and an internal ridge of this part, enclosing a concavity or groove
between them. The head of the radius in its external extension
has overpassed the external ridge, and embracing it, has formed
an interlocking fixed articulation. The interior face of the head
of the radius has also applied itself exactly to the median groove
of the ulna, forming another fixed key joint of much firmness.
The articular face of the head of the radius has naturally formed
a ridge in adaptation to this groove of the ulna, as well as to
the groove of the humerus which corresponds to it. Opposite

182 COPE. (Vou. III.

the two crests of the ulna the articular surface of the radius is
naturally concave, receiving the convexities of the humeral con-
dyle. The external cotylus has become a groove corresponding
to a crest of the humeral condyle, which has been developed by
gradual modification of a strong convexity, such as is seen in
Anoplotherium and Oreodon, and the Condylarthra (Plate I.
Fig. D), and which is characteristic of many Unguiculata. Its
keel or tongue-like character may be ascribed to the action of
torsion combined with impact, as we find to have been the case
with the distal metapodial articulations. It has been homologized
with the intertrochlear crest of the Anthropomorpha, but it is
not homologous with it. It is homologous with the external
condyle or trochlea, while the crest of the Anthropomorpha is
really intertrochlear. The condyle is developed extad of this
keel, coextensively with the head of the radius. The develop-
ment of these two extensions is necessarily coextensive, since
they are mutually dependent on each other for their growth
stimulus. Judging by the character of Hyracotherium ventico-
Jum, the external extension commences with the head of the
radius, since the external condyle of the humerus is much more
retreating proximad than it is in the species of Equus. It has
developed distad in the latter, genus, so as to bear nearly the
same transverse line as the internal condyle (Plate I. Fig. E).
The mechanical cause of the origin of this peculiar external
roller of the distal humeral condyle is the same as that which
has given origin to a similar structure on the external sides of
the distal extremities of the metapodial bones. This is the ex-
cessive use consequent on the very frequently externally diver-
gent relation of the distal to the proximal element in the case;
here, of the fore arm on the humerus. This occurs constantly
in the most rapid movement of a diplarthrous Ungulate. On
alighting on the ground at the end of a leap, the anterior foot
supports the entire weight for a shorter or longer time accord-
ing to the gait, the foot resting below the middle line of the
body. According to Allen? the foot even crosses the middle
line, and rests on the opposite side of that line to which it really
belongs. Thus the remainder of the leg is abducted or bent

1 Tertiary Vertebrata, Cope, Pl. XLIX. 4, Figs. 2, 3.
2 Materials fox a Memoir on Animal Locomotion ; from the Report of the Muy-
bridge work at the University of Pennsylvania, 1888, p. 58.

No. 2. ] THE HARD PARTS OF THE MAMMALIA. 183

outwards on the humerus, the animal being knock-elbowed in
this act. The effect of this position during impact is to extend
both radius and humerus outwards, and to push from its primi-
tive position that one of the
two elements which has the
least longitudinal support
(Fig. 23).

The history of the elbow-
joint in the Lagomorphous
Rodentia is the same as that
which I have described in the
Diplarthra, excepting that the
applied surfaces of the head
of the radius and the ulna do
not mutually interlock. The
expansion of the head of the
radius is identical in the two
cases, as is the form of the
condyles of the humerus, in-
cluding the trochlear crest
and the extension external to
it (Fig. 42).. This is an ad-
mirable illustration of the pro-
duction of lrke effects by like
causes, in two widely different

lines of descent. figure 23. — Cervus canadensis, trot-
The elbow joint of the bat ting, from behind; from Muybridge, Ani-
has some points of resem- mal ESEOmOrOn; showing position of fore
Planecito thateotithe higher foot in support of the body.
Diplarthra and Rodentia. The ulna is reduced to a splint below
the proximal part of the radius, to which it is not co-ossified,!
and the olecranon is represented by a sesamoid bone in the ten-
don of the extensor muscle. The humeral condyle is developed
external to the external convexity, but the internal condyle has
no extension beyond the flange, thus differing from Bovidz and
Leporide. In Pteropus and Vespertilio the ulnar groove of the
humerus is not deep. In Pteropus the external convexity of the
condyle is wide; in Vespertilio it is narrowed into a weak troch-

1See W. Leche, Ueber der Entwickelung des Unterarms u. Unterschenkels bet
Chiroptera. K. Svenska Akad. Handlingar, V., 1879.

184 CORE. FVow. TUE.
lear crest. In Rhinolophus (Plate I. Fig. C) the trochlear crest
is prominent and acute, and the intertrochlear groove is deep.

The head of the radius does not extend internally to the exter-
nal crest of the external condyle, which is here much like the

ee J

S we
a U
Me
Ph

Figure 24.— Anterior limb of bat.

flange of the Carnivora. The high development of this elbow-
joint in the Chiroptera cannot of course be ascribed to impacts,
but it may be ascribed to an equally effective cause, viz., the
great mutual pressure of the parts, accompanied by torsion,
when in action. The muscular tension during flight is very
great, and inequalities already existing in the surfaces of the
bones forming the articulation would tend, under the influence
of torsions, to be exaggerated. The external and internal con-
dyles of the humerus were already distinct in the ancestors of
the bats, of which Galeopithecus may be regarded as the nearest
living ally. The pressure of the tendon of the triceps extensor
muscle, with its sesamoid bone, has tended to deepen the inter-
trochlear groove.

The elbow joint of the mole presents peculiarities of its own.
The manus is incapable of supination in the usual way, but it
reaches a position half-way between pronation and supination in
the opposite direction ; that is, by the rotation of the distal end

No. 2.] THE HARD PARTS OF THE MAMMALIA. 185

of the radius downwards instead of upwards. This movement
may be called antisupination. In it the palm is presented out-
wards, and, when the humerus is flexed backwards, backwards
also. This is its normal position when pushing the earth back-
wards from its burrow, and the muscles to accomplish this move-
ment are enormously developed. These include the subscapula-
ris, infra. and supraspinosus, and the triceps extensor. The
act of antisupination of the manus is performed by the pronator
muscles of the fore arm, and the effect of the rotation inwards
of the distal end of the radius is to throw the proximal end out-
wards, so that it comes to be as external to the ulna at the coty-
lus, as in a quadrumane. The external condyle of the humerus
is thus especially developed to receive it. In the act of anti-
supination the head of the radius describes a movement in the
transverse direction towards the external epicondyle, and the
external condyle has been extended in that direction as a conse-
quence of the continued thrust.

c. The Femoro-tibial Articulation. The existence of tibia and
fibula of subequal size gave rise to two distal articular surfaces
of the femur. The constant use of these in flexion and exten-
sion gave them the convexity which they possess in the Mam-
malia, a process already commenced in the Reptilia. The strong
tendon of the rectus muscle passing over the anterior face of the
extremity gave rise to the rotular groove. This became better
defined and more important after the development in placental
mammals of a sesamoid bone, or patella, in the tendon. The tor-
sion of the femur on the arrest of the foot by the earth is, as
with the humerus, from within forwards and outwards. To this
cause, plus the impact, we may assign the production of the
crest of the tibia in the same direction. The reason why, in the
Reptilia, the fibula diminished in size, and the head of the tibia
so expanded as to support the greater part of the external con-
dyle of the femur, I am not at present able to suggest.

ad. The hinge between the first and second series of tarsal bones
in the Artiodactyla may be accounted for by reference to the
habits which are supposed to have caused the cloven-footed
character. Observation on an animal of this order walking in
mud, shows that there is a great strain anteroposteriorly trans-
verse to the long axis of the foot, which would readily cause a
gradual loosening of an articulation like that connecting the two

186 COPE. [Vor. III.

series of tarsals in the extinct Amblypoda (Fig. 8). Any one
who has examined this part of Cory-
phodon will see that a little addi-
tional mobility at this point would
soon resemble the second tarsal joint
of the Hippopotami, etc. In the
case of animals which progress on
hard ground, no such cross-strain
would be experienced, and the effect

would be to consolidate by flattening the
fixed articulation. And this is what has
occurred in the Perissodactyla, beginning
with the oldest known forms.

e. The Tarsal Articulations of the Eden-.
tata. The peculiarities of the tarsal artic-
ulations in the Edentata have reference
to the lateral direction of the sole of the
posterior foot in the families Megathe-
riide, (Megalonyx,) Bradypodidz, and
Myrmecophagide. This semisupination

is accomplished in two ways: Ist, by an

Figure 25.— A, Bradypus tridactylus 1, posterior foot, from behind, nat. size:
from Cuvier. B, Cholepus didactylus L., tarsus and end of leg, from behind, natural
size: from Cuvier, Oss. Foss. @, Astragalus with peg and socket articulation of
fibula.

No: 2.

THE HARD PARTS; OF THE MAMMALIA. 187

oblique articulation between the tibia and astragalus ; and second,
by a rotation of the navicular on the rounded extremity of the

astragalus.
second in the Meg-
alonyx and Myrme-
cophaga, and both
combined in the
sloths (Bradypodi-
dz). The incurva-
tune, OL the’ Loot
naturally resulted
from the
amd size of the
claws, which ren-
dered a truly planti-
grade walk difficult
or inconvenient, and
thus compelled the
animal to walk on
the outside of its
fee=’ In’ the mod-
ern sloths the lat-
eral position of the
tibio-tarsa] articula-
tion is an exact adap-
tation to the trans-
verse direction
assumed by the foot
in hanging or walk-
ing while holding
the body suspended
beneath the branch
on which the ani-
mal lives. The di-
rection of the foot is
at right angles to the
longitudinal axis of
the body, and across
the branch to which
it is suspended.

leon othe

SSQ Qo \

The first mode is seen in the Megatheriidz ; the

\
\,

fl
ff
\ woop”

Ws

SS

he.

Figure 26.— Cholepus hoffmanii, in progression;

three positions of the limbs; from Muybridge, Animal
Locomotion,

188 COPE. [Vot. III.

The mechanical causes of these structures appear to be as
follows. The strained incurvature of the foot has rotated the
astragalus outwards on the tibia, so that the latter comes to
articulate with its inner side, which has become continuous with
the superior face by pressure. The stage intermediate between
the normal tibio-astragalar articulation, and that of the sloth, is
seen in Megatherium and Mylodon, where the inner part of the
trochlea is reduced to a rudiment. In Bradypus it has dis-
appeared. The pressure of the tibia has had the effect to throw
the external face of the astragalus against the distal fibular
articulation. In the sloths the articular ligaments connecting
the fibular with the external face of the astragalus have been
continuously strained, and the result has been the elongation of
their more or less circular line of insertion, producing a promi-
nent border which embraces the extremity of the fibula like a
cup. And continual rotation has given the extremity of the
fibula a conical form (Fig. 25 & a).

The movable articulation of the astragalus with the navicular
bone is seen in Megalonyx, Bradypus, and to a less degree in
Myrmecophaga. The foot rotates inwards on the long axis of
the astragalus, which has around head. This structure may
be accounted for by the continued effort to perform the move-
ment which it permits. It is to be noted that on this articula-
tion the articular surface of the head of the astragalus presents
a fossa, or a pit, into which a corresponding prejection of the
navicular fits. The mechanical cause of this structure is to
be accounted for by the ligamentous strain accompanying the
vigorous use of the claws, which these Edentata exhibit in
their habits. But why a rim border should be drawn from the
astragalus rather than from the navicular, I am not able to
explain. The calcaneum is excavated for the head of the astra-
galus, and the sustentaculum is convex; both arrangements
permitting the rotation of the foot plus the calcaneum on the
astragalus.

f. The Tongue-and-Groove Joints. These are the following :

I. Looking downwards.

1. The distal humeral in Artiodactyla and Quadrumana.
2. The distal radial.

3. The distal tibial.

4 and 5. The distal metapodial.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 189

IJ. Looking upwards.
6. The lateral proximal astragalar.
7. The proximal phalangeal.

I premise that the elbow joint comes under this head in the
higher Diplarthra, but not being generally of this character, it
has been already considered elsewhere (p. 179).

The trochlear keels which look downwards are much the
most prominent and important. They are all projections from
the ends of the respective elements. The up-looking are gener-
ally projections of the edges of bones. Such are the lateral
crests of the astragalus, and of the phalanges of the Edentata.
The tongues of the tongue-and-groove articulations exhibit vari-
ous degrees of development in the different Mammalia. Those
of different parts of the skeleton coincide in their condition in
any one type of ambulatory Mammalia, and so may be all con-
sidered together. This fact suggests strongly that they are all
due toacommon cause. The
proximal ridges of the pha-
langes are very weak except

Fic. 27. Fic. 28.

Figure 27.— Right posterior foot of a species of Coryphodon from New Mexico,
one-half nat. size; from Report Expl. W. of tooth Mer., G. M. Wheeler, IV.,
Pl exe

Figure 28.— Right posterior foot of Afphelops megalodus Cope, from Colorado,
one-half nat. size; from Report U. S. Geol. Surv. Terrs., F. V. Hayden, IV.,
Pl. CXXX.,

190 COPE. [Vot. III.

in certain Edentata; and crests on the extremity of the radius
are adaptations to the carpal bones.

The tongues proper are all imperfect in the Rodentia and
Carnivora (Figs. 5, 6) (except the Leporidz, which are especially
characterized by their great speed). Among Ungulates they are
very imperfect in the Proboscidea. The orders mentioned all
have elastic pads on the under sides of
their feet or toes. The same is true of
the lowest types of both the Artiodactyla
and Perissodactyla, the hippopotami and
rhinoceroses. In the Ruminantia the troch-
leze are well developed (Fig. 37) with one
exception, and that is the distal metacarpal
and metatarsal keels of the Camelide (Fig.

Fic. 29. Fic. 30. Fic. 31. Fic. 32.

Figure 29. — Distal extremity of tibia of Amdlyctonus sinosus Cope.

Figure 30. — Distal extremity of tibia of Oxyena morsitans Cope. Both creodont
flesheaters and two-thirds nat. size; from Report Expl. and Surv. W. of rooth Mer.,
G. M. Wheeler, IV., Pt. II.

Figure 31. — End of tibia and astragalus of Archelurus debilis.

Figure 32.— Femur of Mimravus gomphodus. Both carnivores. One-third nat.
size; Mus. Cope.

36). These animals confirm the probability of the completion
of the keels being the effect of long-continued shocks, for they
are the only Ruminants which have elastic pads on the inferior
sides of their digits.

That these processes may be displacements due to shocks
long continued is rendered probable by the structure of the

No. 2.] THE HARD PARTS OF THE MAMMALIA. 1QI

bones themselves. (1) They project in the direction of gravity.
Constant jarring on the lower ‘extremity of a hollow cylinder
with soft (medullary) contents, and flexible end walls would tend
to a decurvature of both inferior and superior adjacent end walls.
If the side walls are wide and resistent, the projection will be
median, and will be prolonged in the direction of the flexure of
the joint. (2) They fit entering grooves of the proximal ends of
corresponding bones. Thesé will be the result of the same appli-
cation of force and displacement, as the protrusion of the inferior,
commencing with a concavity as in the astragalus (E/ephas) ;
becoming more concave (Plate II.), and becoming finally a groove.
(3) When the dense edge of a bone, as in the case of the lateral
walls of the astragalus, is presented upwards, a groove is pro-
duced in the down-looking bone; ¢.g. the lateral grooves of the
distal end of the tibia. (4) When the inferior bones are the
denser, the superior articular face yields; e.g. the distal end
of the radius to the side walls and summits of the first row of
carpals (Fig. 15). (5) All of these descending convexities have
been converted into keels in the line of flexure by the long-
continued torsion produced by the greater or less rotation of
the bone with long axis. They have been thus pinched at all
points of their length during flexures, but especially at their
extremities.

To examine these cases in detail. In the ruminating anima!s
(ox, deer, camel, etc.) and in the horse, among other living
species, the ankle joint is a very strong one, and yet admits of
an extensive bending of the foot on the leg. It is a treble
tongue-and-groove joint ; that is, two keels of the first bone of
the foot, the astragalus, fit into two grooves of the lower bone
of the leg, the tibia, while between these grooves a keel of the
tibia descends to fill a corresponding groove of the astragalus.
Such a joint as this can be broken by force, but it cannot be
dislocated. Now, in all bones the external walls are composed
of dense material, while the centres are spongy and compara-
tively soft. The first bone of the foot (astragalus) is narrower,
from side to side, than the tibia which rests upon it. Hence
the edges of the dense side walls of the astragalus fall within the
edges of the dense side walls of the tibia, and they appear to
have pressed into the more yielding material that forms the end
of the bone, and pushed it upward, thus allowing the side walls

192 COPE. [Vot. III.

of the tibia to embrace the side walls of the astragalus. Now,
this is exactly what would happen if two pieces of similar dead
material, similarly placed, should be subjected to a continual
pounding in the direction of their length for a long period of
time. And we cannot ascribe any other immediate origin to it
in the living material ; but the probability of such origin is mére
probable in such substance, because of the perpetual waste and
repair which are going on, as illustrated by the power which
we see in growth, in repairing damages, and in providing for
new conditions in cases of accident. The inclusion of the
astragalus in the tibia does not occur in the Reptiles, but appears
first in the Mammalia, which descended from them.

The same active cause that produced the two grooves of the
lower end of the leg produced the groove of the middle of the
upper end of the astragalus. Here we have the yielding lower
end of the tibia resting on the equally spongy material of the
middle of the astragalus. There is here no question of the hard
material cutting into soft, but simply the result of continuous
concussion. The consequence of concussion would be to cause
the yielding faces of the bones to bend downward in the direc-
tion of gravity. If they were flat at first they would begin to
hollow downward, and a tongue above and a groove below would
be the result. And that is exactly what has happened. With-
out exception, every line of Mammalia commenced with types
with an astragalus which is flat in the traverse direction, or
without median groove. From early tertiary times to the
present day, we can trace the gradual development of this
groove in all the lines which have acquired it. The upper sur-
face becomes first a little concave; the concavity gradually
becomes deeper, and finally forms a well-marked groove.

The history of the wrist-joint is similar. The surface of the
fore-arm bones which joins the fore foot is in the early tertiary
Mammalia uniformly concave. In the ruminating mammals it
is divided into three fossze, which are separated by sharp keels.
These fossze correspond with the three bones which form the
first row of the carpus or palm. The keels correspond to the
sutures between them. The process has been evidently similar
to that which has been described above as producing the side
grooves in the end of the tibia. The dense walls of the sides
of the three bones impinging endwise on the broad yielding sur-

No. 2.] THE HARD PARTS OF THE MAMMALIA. 193

face of the fore arm (radius) have gradually, under the influence
of countless blows, impressed themselves into the latter. On
the contrary, the surface above the weaker lines between the
bones not having been subject to the impact of the blows, and
influenced by inertia and gravity, remains to fill the grooves,
and to form the keels which we observe.

We now consider the development of the keels and grooves
which appear at
the articulation of
the metapodials

Fic. 33.

Figure 33. — Hind foot of primitive cameloid (Poébrotherium labiatum), showing
grooved astragalus and first toe-bones, without keel, in front at lower end; from Col-
orado.

Figure 34. — Hind foot of three-toed horse (Protohippus sejunctus), from Colo-
rado, showing grooved astragalus, and trace of keel on front of lower end of first bone
of middle toe.

Figure 35.— United first bones of two middle toes of deer-antelope (Cosoryx
furcatus), showing extension of keel on front of lower end; from Miocene of Ne-
braska.

194 COPE. [ VoL. III.

with the bones of the second set (phalanges). These keels first
appear on the posterior side of the end of the first set of bones,
projecting from between two tendons. These tendons, in most
mammals, contain two small bones, one on each side, which act
like the knee-pan and resemble it in miniature, the sesamoid
bones. These tendons and bones exercise a constant pressure on
each side of middle line, when the animal is running or walking,
when extension of the phalanges is most
pronounced ; and this pressure, together
with the concussion with the ground and the
torsion of the limb, appears to have permit-
ted the protrusion of the middle line in the
form of a keel, while the lateral parts have

- been supported and
even compressed.
The reptilian ances-
) tors of the mam-
mals do not possess
these keels.

Figure 36.— Part of anterior foot of Procamelus occidentalis, from New Mexico;
from Report of Capt. G. M. Wheeler, Vol. IV., Pt. IT.

Figure 37.— Metacarpals of Cosoryx furcatus, from Nebraska, two-thirds nat.
size: a, anterior face; 4, posterior; c, proximal end; d, distal end.

Figure 38. — Left fore foot with part of radius of Poébrotherium vilsoni Leidy,
from Colorado, three-fifths nat. size; from Hayden’s Report, III., (unpublished).

No.2] THE HARD PARTS OF THE MAMMALTIA. 195

Now, the lines of mammalian descent displayed by paleontol-
ogy are characterized, among other things, in most instances,
by the gradual elevation of the heel above the ground, so that
the animal comes to walk on its toes. It is evident that in this
case the concussion of running is applied more directly on the
ends of the bones of the foot, than is the case where the foot is
horizontal. As a consequence, we find the keel is developed
farther forward in such animals. But in many of these, as the
Carnivora, the hippopotamus, and the camels, there is developed
under the toes a soft cushion, which greatly reduces this concus-
sion. In these species the keel makes no further progress. In
other lines, as those of the horse, the pig, and of the ruminants,
the ends of the toes are applied to the ground, and are covered
with larger hoofs, which surround the toe, and the cushion is
nearly or quite dispensed with. These animals are especially
distinguished by the fact that their metapodial keels extend
entirely round the end of the bone, dividing the front, as well
as the end and back, into two parts. This structure would seem
to be a result of the greater force of the impact resulting from
use of the legs, experienced by the end and front of the bone,
which receives the blows. In proportion to the degree of digiti-
gradism is the strain on the tendons at plantation and recover.
In running, in the ditigrade Ungulata, the toe is antiflexed so as
to bend at right angles anterior to the metapodial bone, just
before leaving the ground (recover). It is the strain and tor-
sion at this moment that has produced the tongue to the front
of the metapodial. It is also evident that the elevation of the
heel offers the condition for torsion strain on the leg immediately
following contact with the ground. This agency has been espe-
cially considered under the head of the fixed articulations.

The distal phalangeal articulations are usually simply concave,
receiving a median angle from the phalanges distad. This me-
dian concavity is probably the result of the impact on the ground,
of a surface narrower than the excavated extremity, viz. : of the
apex of the unguis. This impact exerts the greatest displace-
ment along the median line or axis of the digit. Apart from
this, however, a determining cause of the simplicity of the pha-
langeal groove is found in the undivided flexor tendon and the
single sesamoid bone, both of which exercise considerable pres-
sure on the median line, when the weight of the body is thrown

196 COPE.
on the extremities of the digits, and
extended.

Especial peculiarity of phalangeal
articulation is to be seen in the Eden-
tata. This consists of the deepening

iit"

\
H]
iN

n{

\

Fic. 40.

Figure 39. — Manis indica; manus natural size;

Figure 40.— Priodontes maximus Kerr, fore

Figure 41.— Priodontes maximus Kerr, pes

[Vot. IIT.

they are thus excessively

CAIN
y 3) we
( \\ »
HN

Fic. 41.

from Cuvier, Oss. Fos.
arm and manus; from Cuvier.

; original,

No. 2.] THE HARD PARTS OF THE MAMMALIA. 197

of the distal groove so as to render the articulations, tongue and
groove, like the tibio-astragalar articulation of Diplarthra. This
structure gives great strength, and an increased protection
against dislocation. It exists in both feet of the Manidz and
Myrmecophagide, and in the anterior digits of the Dasypodidze
which have especially developed ungues (Figs. 37-39). The fact
that the ungues differ in this respect in the armadillos, e.g.
Priodontes maximus, gives us an excellent opportunity for inves-
tigating the origin of the structure. The first and second digits
of the fore foot present perfectly simple phalangeal articulations.
The ungues are slender, and from their position take no part in
excavation of the earth. The ungues of the third and fourth
digits are enormously developed, and are chiefly used in excava-
tion. The phalanges display the tongue-and-groove joints. The
ungues of the posterior foot resemble hoofs in form and func-
tion, and the phalangeal articulations are flat and simple, greatly
resembling those of primitive ungulate Mammalia, except that
they have no trace of keel posteriorly. The close relation of
function to the structure is here obvious. The deep tongue-and-
groove articulation is a consequence of the excessive use of the
digits which exhibit it, in the excavation of the earth. The
mechanical cause of the structure must be in the main similar
to that which gave origin to the tibio-astragalar articulation of
the Diplarthra, but it has acted in the reversed direction ; that
is, the median groove looks downwards and the keel looks up-
wards. This difference is to be traced to the different condi-
tions under which the respective processes commenced. In the
case of the tibia, the extremity was primarily convex downwards,
owing to the codperation of impact with gravity. The distal
extremity of the phalange was originally concave, owing to the
pressure of a median tendon and sesamoid bone. In each case
the continued application of the strain would tend to exagger-
ate the original condition. After a certain extent of arc of the
phalangeal articulation has been reached, the sesamoid bone has
little effect, and the continued growth of the keels must be due
to continued impacts combined with torsions of the digits ; the
impacts affecting most energetically the middle line. The tor-
sion movement would have the effect to compress the keels ex-
actly in the line or arc of flexion and extension, by alternate

198 COPE. [VoL. III.

pressure on their sides, as in the case of the distal keels of the
metapodials.

The relative character of the phalanges of the different feet
seen in Priodontes maximus finds a parallel in the Glyptodontide.
Here the tongue-and-groove articulations are strong on the an-
terior feet, and altogether wanting on the posterior! The
ungues on the former are half-claws, and are evidently usable
for digging, while those of the pes are hoofs, usable only for
support or pressure. The relation of cause and effect is as
obvious here as in the case of the Przodontes.

Finally, the mechanical effect of the torsion strain on the
convexity of a condyle in converting it into a keel, may be
noticed in greater detail. The result mentioned appears in the
distal condyles of the humerus in the Diplarthra, at the distal
extremities of the metapodials in many Mammalia, and in the
phalangeal articulations of fossorial types. The effect of a
twisting motion of a convex or a concave surface when in close
apposition, is to cause pressure and friction on each side of a
central dead-point, which is at the centre of the curve. If these
surfaces change their relative positions in one plane through
flexion and extension, a line of dead points at the apex of the
convexity is free from the pressure and friction which are devel-
oped on each side of it. The greater the arc of movement in
this plane, the more extensive will be this dead line. The great-
est movement in arc results where the one surface has a shorter
arc than the other. The concave surface has the smaller arc in
the three positions named, and has also the greatest movement
in arc, as it is in each case the distal element.

The internal and external sides of the distal metapodial con-
dyles are not similar; a character very distinct in the Artiodac-
tyla (Fig. 42). This is simply due to the unequal pressure
exerted on the two extremities of the condyle by the phalanges,
owing to the divergent direction of the digits when serving as
a support. In the distal end of the humerus the same effect is
seen, the external part of the condyle nearly resembling the cor-
responding part of the metapodial bones. This is traceable to
the same cause, viz.: the divergent position assumed by the
fore arm on the humerus, when the weight is supported on one

1 See Burmeister, Archiv. fiir Anatomie u. Physiologie, 1865, p. 317, Pl. VIII.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 199

fore leg only. This brings the line of pressure through the
external part of both the head of the radius and the humeral
condyle (Fig. 23).

Figure 42.— Cervus elaphus ; A, B, C, humero-radial articulation; 4 and C, with
the radius in position; 4, with radius twisted; D, £, metatarsophalangeal articula-
tion; D, front; /, distal views.

In conclusion, the tongue-and-groove articulations of the
mammalian limbs and their origin may be summarized.

I. /ntertrochlear crest of humerus of Anthropomorpha. Orig-
inated from plastic adaptation to space between head of ulna
and coronoid process of ulna.

Il. Yvochlear crest of humerus of Diplarthra. Originated from
impacts, torsions, and exterior divergence of fore arm on hume-
rus.

III. Sutercarpal crests of radius of Artiodactyla; from plastic
adaptation to intercarpal grooves.

IV. Metapodial keels; from impact, torsion, and pressure of
two posterior ligaments and sesamoid bones, and if unsymmet-
rical, as in Artiodactyla, modified by divergence of digits.

200 COPE. [Vot. III.

V. Proximal phalangeal keels, from impacts derived from
apex of unguis, torsion, and pressure of single median tendon
and sesamoid bone on distal end of proximal phalanges.

VI. Astragalo-tibial keel ; impact and torsion aided by gravity.

VII. 7Ytbi0-astralagar keels ; from pressure of dense edges of
astragalus on spongy end of tibia, with impacts and torsion.

Mi THE AXIS OF THE SEELETOMN:

The discussion of this part of the skeleton falls naturally into
the departments of the skull and of the vertebral column.

I, DHE SKUEE:
a. The Sense Organs.

The modifications in the form of the skull are generally di-
rectly related to the muscular strains to which it is subjected.
The size of the brain cavity is directly as the development of
the brain, especially of the hemispheres. The size of its sense
capsules is directly as the activity of the sense which they sub-
serve. With diminution of the sense of sight the definition
of the osseous orbits grows less and disappears, as in the mole
and other subterranean species. Nocturnal species which are
constantly stimulated by diminished, but not extinguished light,
have acquired large eyes, which occupy large orbits. Species
in which the sense of smell is atrophied have very small nasal
chambers, as the Cetacea.

As regards the modification in the proportions of the skull
in adaptation to the brain and organs of special sense, they can-
not be said to be due to direct mechanical interference of the
latter, in impressing the former. The changes in proportions
are here effected during embryonic life by the change in the
distribution of building material. The brain and organs of
sense are outlined in the embryo before the skull has attained
any rigidity, and the latter may be truly said to be moulded on
the former. We have here an illustration of the effect of
use which is not mechanical, since the softer tissue of the
brain and sense organs cannot coerce the harder tissue of
the skeleton. It shows how that use, whether it effect mechan-
ical changes in the hard tissues or not, produces a distinct

No. 2.] THE HARD PARTS OF THE MAMMALIA. 201

change in the distribution and determination of growth-energy
in the embryo. This sustains the dynamic theory of heredity
which I proposed in 1871, and which was subsequently termed
perigenesis by Haeckel. Sucha hypothesis is equally necessary
to explain the transmission of characters, which are more or less
developed in the adult by the mechanical energy of impacts and
strains.

B. The Muscular Insertions.

As regards muscular insertions, the best marked are those
for the muscles supporting the head on the vertebral column,
and for moving the lower jaw in mastication. Strength of the
former has developed the strong occipital crest of the inion.
Size of the temporal muscle determines the expanse of the
gygomata, and the presence or absence of a sagittal crest.
Forms which move the lower jaw transversely have the tem-
poral muscles inversely as the extent of the lateral excursions
of the jaw. Hence these muscles have a diminished size in
such forms as the ruminants, and are widely separated. On the
other hand, the pterygoid muscles and their osseous insertions
are enlarged. This is still more the case with forms which have
an anteroposterior movement of the lower jaw, as the Rodentia
and Proboscidea, where the pterygoid fossa is very large.

The position of the dental series with reference to the skull
in general has reference to the energy of the action of the
temporal and masseter muscles. In primitive Mammalia a con-
siderable part of the molar series is below and posterior to the
position of the orbit, and the series has been prolonged poste-
riorly in forms which possess the proal or palinal mastication, as
Rodentia and Proboscidea. In forms with ectal or ental masti-
cation, on the other hand, the molar series has gradually moved
forwards so as to be entirely anterior to the vertical line of’ the
orbit, as in the horse and the Bovide. The camel retains the
primitive relation in this respect.1 This apparent anomaly may
be explained by the fact that the camel retains large and pow-
erful canine teeth, which he uses as weapons of offence and
defence, so that his temporal muscles retain the large develop-
ment of the early forms. This is further indicated by the

1 See Kowalevsky Monographie d. Anthracotherium, 1873, Pl. IX.

202 COPE. [Vor. III.

presence of a sagittal crest, the only instance of its presence in
existing selenodont Artiodactyla. The forms of bunodont Artio-
dactyles with the orthal mastication (Elotherium and Dicotyles)
have the molar series posterior ; those with lateral movement of
the lower jaw (Sud@, Phacochwride) have them rather more
anterior. In man, also, the dental series retains its primitive
posterior position, but for very different reasons. The large
development of the cerebral hemispheres has caused the reten-
tion of the primitive foetal flexure of the cranium, and the
anterior part of the dental arcs has even retreated from the
position it occupies in the apes. The non-retreat of the inferior
part of the mandibular symphysis has caused the appearance of
the chin, a feature so characteristic of man.

The use of the canine teeth as organs of prehension in the
Carnivora is directly followed by the abbreviation of the muzzle,
as in the bull-dog, the hyzenas, cats, etc.

The mechanical cause of these various positions may be inter-
preted as follows: In vertical action of the lower jaw, the use
is severe directly as we approach the power; z.e. the point of
insertion of the temporal and masseter muscles. The posterior
teeth will then acquire the greatest development, and will con-
tinue to be erupted at the region of the greatest nutritive
activity, z.e. posteriorly. In the case of the Rodentia there is
another mechanical influence, viz.: the posterior horizontal pres-
sure exerted by the inferior series on the superior. Why the
Proboscidia should retain the posterior position of the superior
molar teeth, while the pressure of the inferior molars is in the
opposite direction, ze. from behind forwards, is not readily
explicable at present. But it is evident that, owing to the
extraordinarily vigorous use to which the superior incisors are
subjected, as in the case of the canines of the Carnivora, that
natural selection would preserve the short-muzzled forms in
competition with long-muzzled ones.

The modification of the skull which the Cetacea and Sirenia
have undergone with the lapse of geologic time, is well known.
In the earliest known representatives of the order Cetacea, the
Zeuglodontide, the external nostrils occupy a point on the su-
perior face of the muzzle approximately half way between the
lines of the premaxillary and anterior frontal borders, and
the nasal bones are elongate. In the Balaenidz the frontal is

INOS 25] THE HARD PARTS OF THE MAMMALIA. 203

crowded back to the parietal, and the latter forms but a narrow
band in front of the occipital, while the nasals form but a short
roof over the nostrils, which are now above the eyes. In the
Delphinidz the nostrils have an even more posterior position,
and the nasal bones take part in the extreme shortening already
seen in the frontals and parietals. The convenience of this
location of the nostrils is evident. It relieves the animal of the
necessity of raising the muzzle from the surface of the water in
taking an inspiration ; a convenience which becomes a necessity
in the two families last named, when the cervical region has
become so short as to render such a movement impossible.

The mechanical energy which has caused this posterior retreat
of the nostrils appears to me to have been the constant pressure
of a column of water from below, z.e. from the mouth. This
constant discharge through the nostrils appears to me compe-
tent to force the oblique superior wall of the nasal canal to
become a vertical one, and to shorten the nasal bones from
before backwards, until they cease to obstruct the outgoing
current.

y. Lhe Horns.

Horns are developed in Mammalia and other Vertebrata on
similar parts of the skull, principally on the posterior lateral
angles, as in various Batrachia, Reptilia, and Mammalia, and on
the nose, as in a few Mammalia and several reptiles, recent and
extinct. These parts are the ones which are especially brought
into contact with resisting bodies; the nose in pushing a path
or way for the head and body; the lateral occipital region in
defence and assault, when the sensitive nose and eyes are pro-
tected by being held near the ground. In the latter position
the postero-lateral angles, when present, receive more frequent
collision with, and vigorous stimulation from, a body attacked or
resisted, and in accordance with the observed results of irrita-
tion on dermal and osseous tissues, additional matter has been
deposited. In Lacertilia and Batrachia Salientia there are dis-
tinct postero-external cranial angles ; in Batrachia Urodela such
angles are less prominent. In Unguiculate Mammalia and in
all others with a sagittal crest there are no such angles; hence
this type of skull has never developed posterior horns. The
rhinoceros has developed the dermal nasal horn, and the Elas-

204 COPE. (Vou. IID..

motherium, a median osseous horn, since postero-lateral angles
of the skull are wanting. In the Dinocerata and the Artiodac-
tyla, where the temporal crests are lateral, leaving a wide fronto-
parietal plane with posterior lateral angles, horns are devel-
oped. In members of both groups horns have been developed
over the orbits also (Fig. 43), and in the Dinocerata on the ex-
tremities of the nasal bones as well. These growths are all on
parts which are subject to especial irritation by contact with
other bodies, animate and inanimate.

Among Artiodactyla, the deer (Cervide) are especially dis-
tinguished by the periodical shedding of all but the bases of
their horns. Extinct forms found in the Upper Miocene of the
United States and France (the Loup Fork series) furnish the
explanation of the origin of this remarkable peculiarity. In the
genus Cosoryx we find that the horns may or may not possess
a burr near the base of the beam, like that of the deer; the
same species being indifferently with it or without it. This
observation has been made on three species, —the C. necatus,
C. furcatus, and C. ramosus. The following explanation of these
facts has been proposed by myself.! “From the facts of the
case the followmg inference may be derived, premising that it
is very probable that a genus allied to the present one has given
origin to the family of the deer. It is obvious that the horns
of (Dicrocerus) Cosoryx did not possess a horny sheath as in
the Bovide, from the fact of their being branched. As the
sheath grows by addition at the base, the presence of branches
which necessarily obstruct its forward movement, would be
fatal to the process. There is much to be said in favor of the
view that the horns were covered with an integument, probably
furred, as in the giraffe and young stage in the deer. Thus
there are grooves in the surface of the beam for superficial
blood-vessels, which must have been protected by skin (I do
not observe these grooves on the beam of C. ¢eres). The reten-
tion of the broken extremity of an antler, so as to be reunited,
as described (Fig. 43, 3), could not have been accomplished
without an integument. The presence of the burrs cannot be
accounted for on any other supposition, as there are no foramina
to give exit to nutrient vessels at the point where they exist ;

LU. S. G. G. Survey west of the 100th Mer., G. M. Wheeler: iv., Paleontology,
1877, p. 348.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 205

the irregularity of those positions also forbids the latter idea,
and adds to the probability that the arteries which furnished the
deposit of phosphate of lime were contained in a superficial
dermal coating. The supposition is also strengthened by the
fact that the only existing Ruminants (the giraffes) with per-
manent horns without horny sheaths have them covered with
hairy skin.

“Tt appears that in the antlers of Cosoryx the deposit of a
burr was immediately associated with the death of the portion
of the horn beyond it, so that it disintegrated and disappeared.
This was not the case
with the beam in the
specimens observed.
Nevertheless it is
probable that the
death of the horn
would be associated
with the deposit of
the burr in this case
also, were the condi-
tions the same. What
those conditions were
we can only surmise.
It was very probably
the death of the in-
tegument which _ in-
vested and nourished
the horn that pro-
duced that result;
and this would more
readily occur in the Z@
exposed antlers than
in the more protec- .
ted basal portion of
the beam. It is very
probable that this re- ad
sult would follow Figure 43.— 1, 2, Cosoryx necatus Leidy; 7, with-
blows and laceration out, 2, with, burr on antler; 3, 4, Cosoryx ramosus

Cope; 3, antler broken and reunited; 4, beam with
of the surface re- burr; two-thirds nat. size; original; from Report U.
ceived during com- §, G. G. Expl. 1ooth Mer., G. M. Wheeler.

206 COPE. [Vot. III.

bat, or accidental contact with hard substances. The integu-
ment would be stripped up to near the junction of the antlers
with each other, or of the beam with the cranium, and the
arteries would be constricted or closed at those points. It is
near these junctions that all of the burrs are found. But as
such lesion would be necessarily less complete at the point
where the horn has greatest circumference, so the entire death
of the horn might be less usual than that of the branches.
Should such lesions have occurred for a long period at the
breeding season, nature’s efforts to repair by redeposit of bony
tissue might as readily become periodical as the increase in
size and activity of the reproductive organs and other growths
which characterize the breeding season in many animals. The
subsequent death of the horn would be at some time followed
by its shedding by the ordinary process of sloughing.”

Cosoryx is not the true ancestor of the Cervida, as its teeth
have already attained the prismatic type of the higher Bovide.
But Blastomeryx is most probably the ancestor of the deer.
The remains of this genus occur with those of Cosoryx, but the
burr has not yet been observed on its horns.

2. THE VERTEBRAL CENTRA.
a. The Articular Faces.

The mutual articulations of the vertebral column are these of
the centra and of the zygapophyses. Many important modifi-
cations in these articulations are to be seen in Vertebrata,
the Reptilia presenting the greatest variety, excepting in the
zygapophyses, which are tolerably uniform in that class. In
the Mammalia modifications of the central articulations are not
more striking than are those of the zygapophyses.

The forms of central articulation are four ; viz.: the amphicce-
lous, the ball-and-socket, the plane, and the saddle-shaped. The
first type is only seen in a very imperfect degree in Mam-
malia and in but very few vertebrze, where it is indeed but a
modification of the plane. The ball-and-socket is chiefly found
in the neck of long-necked Mammalia, as the higher Diplar-
thra, and to a less degree in their lumbar regions, while the
dorsal vertebrze present an approach to the same type in the
same groups. The saddle-shaped centrum is only found in

No. 2.] THE HARD PARTS OF THE MAMMALIA. 207

Mammalia in the necks of certain genera of monkeys. The
majority of Mammalia present the plane articulation of all the
vertebral centra.

In Mammalia in which movement of the vertebre on each
other has become impossible, the centra codssify. Such is
their condition in the extinct Edentata of the family Glyptodon-
tide, where the carapace is, as in the tortoises, inflexible, and
which therefore limits the possibility of motion of the vertebral
column. Another illustration is seen in the necks of the Balz-
nid Cetacea, and to some degree in the Delphinidz and Physe-
teridz. The lack of present mobility of this part of the column
is due to its extreme abbreviation, a character which has been
gradually developing during Czenozoic time; since the earliest
Cetacea had considerably longer necks than the later ones, and
had their vertebral centra distinct. I cannot account posi-
tively for this shortening of the neck, but will make a sugges-
tion which may prove to be sufficient. It appears to me
probable that the shortening was the result of disuse. This
disuse would arise from gradually increasing powers of locomo-
tion through the water, a progress which, judging from the
character of the limbs of the Zeuglodon, was evidently made
after the time of the Eocene. The increase of speed would
enable the animal to overtake and capture its prey, without the
necessity of using a long prehensile neck in seizing it in the
pursuit.

The ball-and-socket articulation of the vertebrz is well known
to be the predominant condition in the Reptilia, and the fact
that it is necessarily associated with the flexibility of the column
is equally well understood. This flexibility is directly as the
weakness of the limbs, for in the large terrestrial Reptilia of
the order Dinosauria, the vertebral articulations of the dorsal
region, at least, are plane. That it is chiefly confined to, and
best developed in, the most flexible regions of the column of the
Mammalia also shows this necessary connection. There can
be no doubt but that the ball-and-socket vertebral articulation
has been produced by constant flexures of the column in all
directions, as has been suggested by Marsh.

The saddle-shaped articulation permits great lateral and verti-
cal flexure, but none in any other direction. Longitudinal
torsion is impossible. It is a more secure articulation than the

208 COPE. [ VoL. III.

ball-and-socket, and admits at the same time of more abrupt
flexure than the latter. It may have arisen in birds from a
combination of two causes. One of these is the much greater
frequency of the vertical and
lateral flexures of the cervical
region than any others. These
are seen in the vertical flexure
of the neck when in ordinary
repose ; and the horizontal flex-
ure when the head is placed
under the wing during sleep. A
greater tension of the interver-
tebral ligaments than is found
in cold-blooded or even other
warm-blooded invertebrates,
would encourage an especial ac-
tivity of nutrition in the regions
of greatest stress, when the col-
umn was flexed in the two habit-
ual directions, and thus the edges
of the primitive cups be drawn
out in the directions in which
we findthem. This would seem
to be a reasonable explanation
of the origin of this type in birds,
and it may apply to the cervical
region of the monkeys, which
display it. They frequently sit
with the head resting on the
shoulders and the neck bent
in an anteroposterior sigmoid.
Whether they lean the head to
one side or on the shoulder, dur-
ing sleep, I have not had the
opportunity to observe.

The plane vertebra, like the
other types, was derived from the biconcave or amphiccelous,
by ossification of the intervertebral cartilage. This cartilage is
divided, each half forming the epiphysis of a centrum (Hoff-
man), and in the Mammalia without forming a ball-and-socket

Figure 44.— Cervical vertebrae of Cynocephalus, showing saddle-shaped centra,

No. 2.] THE HARD PARTS OF THE MAMMALIA. 209

joint. This was clearly for the reason that movements of the
vertebral column were not necessary for locomotion, which was
performed by the aid of stout limbs, on land.

B. The Relative Lengths of the Vertebre.

The extreme abbreviation of the cervical vertebrz in the
Cetacea has been already referred to, and a cause suggested.
Tais is the disuse naturally following increased power of turn-
ing che body about in the medium in which they live. As a
matter of fact the inverse relation between the two functions
may be observed in many marine Vertebrata. Such are fishes
in general, marine turtles, and Ichthyosauri. A few fishes
(Dercetidz) and the Plesiosauri had long necks, but these
animals may be supposed to have used their necks in exploring
holes in reefs or the shores and bottom of the ocean.

Great elongation of the tail and neck is found in certain types ;
the former especially in some Edentata (Manis) and Rodentia,
and the latter in Artiodactyla. Length of tail may be regarded
as an inheritance from, or reversion to, Reptilian ancestors ;
but length of neck is a direct adaptation to the habits of the
animal, and is always correlated with length of the fore legs.
In animals which take their food from the ground it is not diffi-
cult to see in it a result of strains in the long direction, aided
by gravity, as in the Hyanas and Artiodactyla; but in those
which browse like the giraffe, the mechanical conditions are
different. I cannot demonstrate the correctness of the view of
Lamarck that the enormously long neck of the giraffe was
produced by continuous stretching upwards. Muscular contrac-
tion can only result in the straightening of che neck and
limbs, but not in the application of any extensor energy. For
the present we may suppose that the mere effort of straighten-
ing the limbs and neck long continued would be equivalent to
use and would determine nutrition to the parts. With the
straightening would occur numerous lateral strains, which would
conduce to the same result.

In the Hyzenas the case is clear. The fore legs and neck are
subjected to especial strain in their mode of feeding. After
Canidz and Felidae have deprived a carcass of much of its
flesh, the Hyzenas devour the skeleton and ligaments. Their

210 COPE. [Vot. III.

task requires much more force for its execution both in the fore
legs and feet in holding the bones to the earth, and in the neck
in dragging them asunder; while the task of comminuting them
is performed by the large sectorial molar teeth, the most power-
ful and massive in the entire order of Carnivora.

3. THE VERTEBRAL ARCHES.

The mechanical cause of the origin of neural spines may be
traced to the strains upon the vertebral axis caused by a pri-
mary dorsal fold or fin; and in later and terrestrial types, to
the strains imposed by the presence of the dorsal muscles. The
existence of diapophyses may be perhaps assigned to the strains
from the two primitive lateral folds from which the pectoral and
ventral fins were evolved. The zygapophyses occupy the space
on the vertebra, between these two fulcral points, and constitute —
an important element in the interlocking of the vertebra. Of an
efficient mechanical cause for their origin we are ignorant, and
the search for it would more appropriately belong to the inves-
tigation of the lower vertebrata than to the present paper. I
only recall here that the crests of the zygapophyses are the seat
of the insertions of a part of the mz/tifidus spine muscle, and
receive its strains.

Mammalia present important peculiarities of the zygapophy-
ses. That these are well-marked may be derived from the
accompanying plates III.-VI. The primitive form of simple
flat surfaces prevails in the lower orders, offering only differ-
ences in their greater or less obliquity. In Manis, the Creodonta,
and the Ungulata, this obliquity assumes an interlocking char-
acter. The prezygapophysis becomes concave in transverse
vertical section, forming an anteroposterior canal, while the post-
zygapophysis becomes a partial anteroposterior cylinder, which
fits within the former. In the Artiodactyla the structure is fur-
ther modified in various genera. In Sus and Capra as extreme
examples, the postzygapophysis becomes sigmoid in transverse
section, its external surface displaying a longitudinal cylinder
below, continuous with a groove above, the whole surmounted
by the overhanging edge of the roof of a process, or episphen.

Since these structures appear only in the lumbar region, where
motion is possible owing to the absence of rib connections, and

No.2.) THE HARD PARTS OF THE MAMMALIA. 211

where the greatest weight of the body is supported, we are
at once directed to strains as their cause. We cannot trace
them to vertical strains, since the semi-cylinders and their em-
bracing channels are perfectly horizontal, and not bent so as
to permit vertical flexure of the column. They are not due to
lateral curvature of the column, for then each cylinder would be
convex externally in the longitudinal direction, or perhaps much
abbreviated anteroposteriorly. They appear to have been caused
rather by longitudinal torsion of the column.

Figure 45.— Diagrams representing the movements of the vertebral column in 4,
the pace; 4, the run; and C, the trot or walk.

The mechanical cause of this torsion is as follows. Viewed
from the standpoint of their mechanical effects on the skeleton,!
the gaits of animals may be referred to three types. The first
is that in which the both feet of a pair strike the earth together,
and in alternation with those of the other pair when it is used.

1 Dr. Harrison Allen (AZemotrs for a Memoir on Animal Locomotion, 1888, p. 37)
divides the gaits of quadrupeds differently, and apparently with reference to the order
of innervation of the limbs in motion; that is, in accordance with their mode of co-
operation. From this point of view Dr. Allen refers all gaits to two types, syachiry
and heterochiry. In the former “ the right and left foot of a single pair act together,”
whether synchronously or alternately. In hetrochiry, locomotion is accomplished
by “ combination of hind and fore feet,”

212 COPE. (Vor. III.

The typical gait of this class is the run or the jump. In the
second class the limbs of one side strike the ground at the same
time, and alternate with those of the opposite side. This class
is represented by the pace. In the third kind of locomotion the
opposite feet of different pairs strike the earth together, the line
of identical movement being diagonal to the long axis of the
body. The trot is typical of this kind of gait. The majority
of gaits do not conform pre-
cisely with these definitions,
two feet rarely striking the
ground at actually the same
moment, but their mechani-
cal action can be shown to
be predominantly or entirely
of the three kinds. The ef-
fects of such action are as
follows. In the simultaneous
elevation and depression of
the limbs of one pair, alter-
nating with similar move-
ments of the other pair, no
torsion of the vertebral col-
umn results. Inthealternate
elevation and depression of
the limbs of one side in co-op-
eration, the vertebral axis is
alternately depressed and
raised again throughout its
length on one side at one
time. It is rapidly rocked
from one side to the other
during the pace and similar
gaits, and here, also, there is no torsion. When the column
is supported on opposite sides at its two extremities, as in
the trot, it is rocked in opposite directions at the extremities.
Thus, when one side is elevated anteriorly, it is depressed pos-
teriorly, and wece versa. This motion produces torsion of the
column, and especially of that portion which is free from fixed
connections and braces, viz. : the lumbar region. Now an exam-
ination of the gaits of animals shows that it is those which trot

Figure 46. — Cervus canadensis trotting;

from Muybridge, Animal Motion.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 213

which display the involuted zygapophyses, viz.: the higher
Diplarthra. These animals have other gaits also, but they can
and very usually do, trot. The mammals which do not display
this character of zygapophyses rarely or never trot. Thus the
Carnivora pace and run. The Proboscidia pace. In some of
the mammals of small size the trot may be observed, as in some
Rodentia, but in some of these at least we can conceive that
their insignificant weight does not permit sufficient strain to
affect the form of the osseous material. From the standpoint
here adopted, we must suppose the Creodonta to have used the
trot as their principal gait. (See Plate IV., Fig. 1, lumbar verte-
bra of Mesonyx.)

I refer here to an exception to the above rule which I can-
not satisfactorily explain. While Carnivora are pacers, the
Canidz are to a considerable degree exceptions to the rule.
They trot, or more frequently employ a gait between a pace
and a trot; z.¢. in which the feet of one side are raised consecu-
tively, yet not so as be synchronous with those of their diagonal
opposites as ina trot. Since the Canidze are the ancestral Car-
nivora, and nearest the Creodonta, (having close relations with
the Miacidee), it is natural that they should retain more or less
of the trot of that suborder. The involution of the zygapophy-
ses has however entirely disappeared, a peculiarity which has
yet to be accounted for.

Although the cervical vertebrae of Mammalia undergo con-
siderable torsion, their zygapophyses are flat. But the torsion
has little force, from the fact that these vertebra sustain no
lateral weight.

Besides the zygapophyses, the vertebrata possess the zygo-
sphen, the hyposphen, the episphen, and the zygantrapophysis ar-
ticulations.! The zygosphen and hyposphen are nearly unknown
among Mammalia, but the episphen and the zygantrapophysis
are found in the American Edentata. The episphen is a pos-
terior prolongation of the roof of the neural arch above the
postzygapophyses, from which it is separated by a notch. It is
really a portion segmented from the roof of a zygantrum. The
zygantrapophysis is a prolongation of the superior surface
of the postzygapophysis, and is directed posteriorly. In the
American Edentata it bears an articular facet on its upper

1 Proceedings Amer. Philosoph. Society, 1883, Pp. 545.

214 COPE. [Vou. III.

side, opposite to a corresponding facet on the lower side of the
episphen. These two articulate with corresponding facets of
an anterior prolongation of the metapophysis of the vertebra
next posterior! In the Priodontes maximus the transition be-
tween the normal articulations and those just described may be
observed as we pass from the anterior dorsal region posteriorly.
First the roof of the neural arch projects anteriorly beneath
the arch of the preceding vertebra, forming a zygosphen of a
very depressed type, combined with the prezygapophyses. The
postzygapophysial surfaces are also continuous with the inferior
side of the neural arch, or zygantral surface. The zygapophysial
surfaces soon become distinct, but are not supported by distinct
processes anterior to the last lumbar and first sacral vertebrae.
The metapophyses begin to develop well anteriorly on the dorsal
series, but they do not articulate with the zygantrapophysis in
front of them until the sixth dorsal. On the seventh dorsal it
joins a single large facet above and external to the postzyga-
pophysis. On the eighth this facet, z.e. the roof of the neural
canal, is deeply fissured by an uplooking ridge which separates
the prezygapophysis from the zygosphen, and the episphen has
its origin. On the ninth vertebra this ridge widens, and on the
eleventh and twelfth it becomes distinctly part of the base of
the metapophysis, which articulates above with the episphen,
and below with the zygantrapophysis.

This succession of development of these articulations proba-
bly indicates the manner of their orign. Both the episphenal
and zygantrapophysial articulations are due to the splitting of
the roof of the neural arch on each side behind, by a keel of a
zygosphenal plate which underruns the usual roof from the
vertebra behind. It is a significant fact that this splitting, ze.
the development of the angular ridge on each side the zygo-
sphenal roof, first appears in both the anteater and armadillo,
on the first vertebra which is disconnected with the sternum, or
without hemapophysis ; and which is therefore susceptible of
the greatest amount of vertical movement. The prolongation
of this ridge is really the prolongation of the base of the meta-
pophysis.

We can now, I believe, associate this peculiar vertebral struc-
ture as an effect with anteroposterior strains as a cause, in these

1 Flower, Osteology of the Mammalia, 1885, p. 62.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 215

animals. In the first place, the effect is not due to the meta-
pophysis, but to the anterior extension of their bases. This is
demonstrated by the fact that the articulations are equally
developed in the anteater and in the armadillo, although in the
former animal the metapophyses have not the enormous length
that they have in the latter. That they are due to anterior
extension of the base is shown by the fact that in various mam-
mals where they are developed as largely as in the anteater (e.g.
the mole), but where they have the usual position, the additional
vertebral articulations do not exist. In TZalpa europea the
metapophysis overlaps the neural spine of the vertebra in front
of it very little. In both Myrmecophaga bivittata and Priodontes
maximus its anterior extremity is opposite the anterior border
of the neural spine of the vertebra in front. The anterior trans-
ference of the metapophyses could then only have been accom-
plished by longitudinal muscular strain. This would be pro-
duced by strong upward curvature of the column, especially of
its lumbar region, and strain on the intervertebral ligaments and
muscles. The zygosphenal arched plate would be thus produced,
its effect being to protect the spinal cord, while the neural arches
were strained apart. The metapophysis, as an important mus-
cular insertion, would be subjected to an anterior drawing strain,
which would cause its base to advance with the advance forwards
of the neural arch, and finally to notch, and at last to divide the
arch in front of it, by pressure caused by its apex on the straight-
ening of the column, thus cutting off the episphen. This action
would be distinctly aided by the increasing width of the meta-
pophysis at the base, which spreads the zygapophysial faces out-
ward and produces a longitudinal angle in the lateral parts of
the surfaces in contact, cutting off the zygosphenal from the
zygantral surfaces.

We find that just such flexure of the vertebral column as is
above inferred, is a characteristic habit of most Edentata, espe-
cially of the anteaters, armadillos, and pangolins (Manidz).
They roll themselves into a ball-like form, and retain the posi-
tion against attack with great energy. But here we are con-
fronted by the fact that the Manidz possess this habit, and yet
totally lack the complex vertebral articulations of the American
Edentata (Xenarthri). If we refer the energetic flexures of the
vertebral column to fossorial habits, we are met by the same

216 COPE: [Vot. III.

difficulty ; the Manidz are very similar in this respect to the
Anteaters. The same is true of the African Orycteropus. In
spite of this embarrassing circumstance, I cannot but think that
the explanation of the xenarthrous structure above offered is the
correct one, and we only require more knowledge of the phylog-
eny of the Old World Nomarthra, and of the habits of all the
forms, to learn the cause of this discrepancy. One of several
possible explanations may turn out to account for it. Such
might be the recent adoption of the habit of rolling on the part
of the Manidz; or the feebleness of the species of that family
forbidding their growth energies to respond to the stimulus. Or,
on the other hand, the existence of some habit of vertebral flex-
ure in the ancestors of the existing Xenarthri, which is unknown
to us, may be the cause.

4. THE SCAPULAR ARCH.

®

There is aclose relation between the condition of the Mam.-
malian clavicle and the use of the anterior limb. As a primitive
element of the vertebrate skeleton, Mammalia naturally inherit
it from their reptilian ancestors. Its absence in many of the
former may be attributed to disuse. The use of the clavicle is
to strengthen the scapular arch in the transverse direction ; that
is, against lateral strains both of pulling and pushing, which
come almost entirely from the use of the anterior limbs. In
Mammalia, where the use of the limbs, and consequently the
direction of strain, is vertical, the clavicles are wanting, as in all
Ungulata except Quadrumana. (The condition of the Condylar-
thra as to clavicle is unknown.) In digging mammals the clavi-
cles are generally developed directly as the fossorial power, and
especially as the manner of digging is horizontal or vertical. In
the mole the digging is horizontal, and here the clavicle is ex-
cessively wide and short. In the armadillos, where the move-
ment of the fore legs is vertical, the clavicles are both long and
stout. In Carnivora the clavicle is rudimental, but where pres-
ent the species are vertical diggers. In types of aquatic habit
clavicles are wanting. Such are the insectivorous genus Mytho-
mys, the otters, seals, and the Cetacea. These animals all have
more or less lateral movement of the fore legs, but the resist-
ance of water, the medium in which they move, is greatly less

No. 2.] THE HARD PARTS OF THE MAMMALIA. 217

than that of the earth. In the case of the Quadrumana the
movements of the fore legs are much varied, but include many
transverse strains. The use of these limbs in swinging the
body in all directions when climbing, furnishes ample use for a
clavicle, and cause sufficient to prevent its atrophy.

5. THE PEetvic ARtH.

Modifications of the pelvic arch in Mammalia are seen chiefly
in the form of the ilium and the direction of the pubis.

The ilium differs in regard to the expansion of its proximal
part, and the consequent length of its crest. It is a narrow
bone in Marsupialia and Rodentia, and is a little wider and more
flattened in Carnivora. In Edentata and Quadrumana it is con-
siderably expanded, but the greatest expansion is seen in the
Ungulata which are not Taxeopoda. There is a direct relation
between the form of the iliac plate and the weight that it has
to bear. In the mammals with narrow ilium the abdominal
viscera are light as a consequence of either relatively or ab-
solutely small size. In the types with wide ilia, these bones
support weight either (1) with the length of the crest; or (2)
with the long axis of the plate; or (3) transversely to the long
axis. In (1) the iliac crest supports the huge belly with elongate
viscera, of the Proboscidia, Amblypoda, and Diplarthra, all
herbivorous or omnivorous. In (2) the body is erect more or
less of the time, and the weight of the viscera passes downwards
into the pelvis, spreading laterally against the iliac plates. In
the smaller Edentata this pressure is insignificant, or rarely
felt ; but in the huge extinct forms of the order the Megatheriide,
the customary attitude in feeding was, as Owen pointed out,
obliquely erect, leaning against the trees, or reaching upwards
to obtain their branches and foliage. In the Quadrumana, the
most constantly erect species, man, has the most widely ex-
panded ilia. In (3), the only representation is the family of the
sloths. Here the ilia bear a part of the viscera, directly, as
the animal hangs suspended from the limb of a tree.

The only noteworthy peculiarity of the pubis is the posterior
direction which it presents in the Edentata. This character is
traceable to the semi-erect position of the ancestors of the

218 COPE. (Vox. Tr.

present forms, the Megatheriide. Their long pubis has been
generally pressed downwards and backwards by the weight of
the viscera, while the short pubis of the Quadrumana has not
experienced any such change of direction. The relation of this
effect to the cause in question is demonstrated by the history
of the Dinosauria and of the birds. In the former, the direc-
tion of the pubis has become downwards and then backwards,
directly as the animals have more or less entirely adopted the
erect attitude, by walking on their hind limbs. The viscera have
been gradually swung backwards from in front of to below the
point of suspension, the acetabulum, by the force of gravity ;
and with the advent of complete bipedism, in the birds, a part
of them have moved even posterior to this point, thus more
perfectly maintaining the balance in progression.

A similar posterior direction of the pubis exists in the Tal-
pide. We may with some probability ascribe this to the con-
stant pressure on the abdomen upwards and backwards, which
their mode of life entails on them. The viscera and pelvis are
depressed by superincumbent weight, and the forward movement
of the body in progression furnishes the pressure in the poste-
rior direction.

PL THE DENTITION

The distinction of teeth into incisors, canines, and molars
appears independently at various points in the line of Verte-
brata. Incisors and molars are distinguished in Sparoid fishes,
and in Placodont and Diadectid reptiles. Canine-like teeth, or
pseudo-canines, appear in Clepsydropid and Crocodilian reptiles,
and in Saurodont fishes. Canine-like incisors appear in the
Clepsydropide. The variety of character in these structures
presented by the Mammalia to be considered here is great, and
the principles deduced from observation of them are applicable
to the Vertebrata in general.

As mechanical causes of the origin of dental modifications, I
enumerate the following : —

I. Increase of size of a tooth, or a part of a tooth, is due to
increased use, within a certain maximum of capacity for in-
creased nutrition.

II. The use and change of direction of a tooth take place

No. 2.]} THE HARD PARTS OF THE MAMMALIA. 219

away from the direction of greatest, and in the direction of least
resistance.

III. It follows, from their greater flexibility, that crests of
crowns of teeth yield to strains more readily than do the cusps.

IV. The increase in the length of crests and cusps in all
directions, and therefore the plications of the same, is directly
as the irritation from use to which their apices and edges are
subjected, to the limit set by the destructive effects of such
use, or by the recuperative energy of nutrition.

V. The direction of growth of the branches of a V, or of the
horns of a crescent, will be the direction of movement of the
corresponding parts of the opposite jaw.

1. THE ORIGIN OF CANINE TEETH.

The origin of canine, pseudocanine, and canine-like incisor
teeth is due to the strains sustained by them on account of
their position in the jaws at points which are naturally utilized
in the seizing of prey, or the fighting of enemies. In some
reptiles (Dimetrodon) the end of the muzzle has been utilized ;
in Crocodiles the side of the jaw; while the intermediate posi-
tion has been most used by Mammalia. The reason why the
canine instead of the incisor teeth have been selected by car-
nivorous Mammalia for prehensile purposes is not at present
clear to me. In accordance with Rule [, its increased size has
been due to the especial and energetic strains to which it has
been subjected while in use as a prehensile or offensive weapon,
when buried in the body Of its prey or enemy. The superior
canine would acquire larger size earlier in time than the inferior
canine, since it bears the greater part of such strain, as attached
to the more fixed head and body of its possessor. The anterior
teeth of the lower jaw would be less available for use, since
they offer weaker and less fixed resistance to the opposing
body. That the first tooth behind the canine was not generally
enlarged is (under I.) due to the fact that its posterior position
prevents it from having the same amount of use, and experi-
encing the strain that a tooth more anteriorly placed necessarily
receives. It is excluded from considerable use by the project-
ing muzzle above and.in front of it.

That the increased size of canine teeth is due to strains is

320 COPE: [Vot. IIf.

strongly indicated by the huge development of these teeth in
the walrus. This animal uses its canines for the breaking of
ice, and for lifting itself from the water onto the edge of strong
ice. The fact that canines and not incisors have been thus
developed is a necessary result of the fact that the walrus is
a descendant of a line of animals which had already reduced
incisors and larger canines.

Figure 47.— Nimravus gomphodus Cope, two-fifths nat. size; left side of skull;
from Miocene of Oregon.

2. DEVELOPMENT OF THE - INCISORS.

The history of the incisor teeth of the Mammalia exhibits
three processes; viz.: hypertrophy (e.g. Rodentia), specializa-
tion (e.g. Galeopithecus, Lemuridz), and atrophy (e.g. Booid-
ea, Phacochoeris, etc: ).

Of hypertrophy we have two types: the first represented by
the Rodentia, Multituberculata, Tillodonta and their ancestors ;
and second, by the Proboscidia, the narwhal and certain Sirenia.
As the uses of the incisors present two types corresponding
with their structure, we have ground for believing the uses in
question to have been the efficient agent in producing the latter.
Esthonyx furnishes us with an example (Fig. 48) where all the
incisors are present in the lower jaw, and where the function of
one pair of them (the second) has evidently been partially rodent

No.2.] ZHE HARD PARTS OF THE MAMMALIA. 221

in character; that is, it has served as a scraper and gouger of
food substances. Persistent use has apparently developed the
size of this pair of teeth, until we find in Psittacotherium (Fig.
49), they have reached =
a greater efficiency,
and that the external
incisors of the lower

jaw have disappeared.

This disappearance
can be accounted for
on the ground of dis-
use, a retirement from
service due to posi-

tion, and the ain-
creased growth of
mcison INo, 2.° In S&S we
Calamodon (Fig. 85)
the first incisor has
become rudimentary
from the same cause,

and in Anchippodus

STA ™Wy-u

SSS

Figure 48. — Esthonyx burmeisteri Cope, denti-
tion: a, profile; 4,superior; ¢, inferior dentition, grind-
it has disappeared al-_ ing faces. Reduced.

together, leaving a
truly rodent incisor
dentition, consisting
of the second incis-
ors only, in the lower
jaw. Continued use
as chisels has devel-
oped these teeth to
the great proportions
seen in such Rodentia
ASHE AStOroides, 1 cic
(Fig. 86).

The use which the Figure 49.— Psittacotherium multifraguin Cope,

Proboscidia and _ Si- mandibular ramus, one-half nat. size: @, profile; 4,
from above.

renia (Halicore) give
their incisors, is, from a mechanical point of view, like that
which the Carnivora give their canines; that is, it consists of
strains transverse to the long axis of the tooth. The elephants

222 COPE. VoL wii:

use their tusks for prying up the vegetables on which they feed,
or for pushing aside the vegetation through which they wish to
pass. The ancestors of the Proboscidia are not certainly known,
but they possessed incisors of enlarged proportions, such as we
find in the Toxodontia and other late representatives of some of
the primitive Ungulata. Use of such teeth in the manner re-
ferred to, without opposition from the inferior incisors, will
account for the tremendous proportions which they ultimately
reached in some of the species of Elephas.

The use made by the narwhal of its single huge superior
incisor, that of an ice-breaker, indicates the origin of its large
dimensions, and its primitive limited use in proportion to its
small beginnings. So with the straight incisors of the hippo-
potamus ; use as diggers has straightened them to a horizontal
from their primitive vertical direction, a change partially accom-
plished in the true pigs (Sus.)

Figure 50.— Lemur collaris, dentition from below and aboye; nat. size; original.

In the Sirenian genus Halicore the upper incisors have been
used in excavating vegetable growths from the banks and bottom
of shallow seas. The transition from three incisors (Prorasto-
mus) to two (Dioplotherium), and to one (Halicore), is identical
with what has taken place in the Proboscidia and Rodentia, and
has resulted in the production of an effective digging tool. In
other genera, whose habits of browsing on soft growing mate-
rials did not necessitate the use of digging incisors, these teeth
became atrophied, as in the manatee and Rhytina.

The inferior incisors of the true lemurs are straight, horizontal,

No. 2.] THE HARD PARTS OF THE MAMMALTA. 223

close together, and of slender form. The canines form part of
the series, and are not distinguishable by external characters
from the incisors. The reason of the peculiar characters dis-
played by these teeth is to be found in their present habits.
These organs are used as combs for dressing the fur, and for
removing parasites from the skin, and the apparatus is a most
effective one. The gradual evolution of this character and its
accompanying function may be traced from the Adapidz of the
Eocene period. In some of these forms (as Tomitherium) the
incisors are quite oblique, and in Adapis the canines are inci-
siform. The mechanical effect of combing the hair with inci-
sors of ordinary structure, would be to first wear off any lateral
expansions of the crowns, and then to narrow their apices. The
strains would also gradually cause a successively procumbent,
and then decumbent direction of the crowns. Lack of use,
owing to lack of opposition of the inferior incisors, would be
followed in the superior incisors by the reduction in size which
characterizes them. I have not seen Galeopithecus in life, but .
I suspect that its very peculiar comb-like inferior incisors are
the product of a similar habit. In this genus, however, the
incisors have transversely expanded crowns, and they are divided
from the edge to near the base by parallel fissures. Thus is
produced a comb, which is as effective functionally as is that
of the Lemurs. I suspect that this result was brought about
by use, on the part of the ancestors of this genus, of incisor
teeth already so expanded as to suffer division rather than con-
traction by the long-continued friction of hair.

The atrophy of incisors is a fact for which mechanical reasons
are not readily found. It has occurred in the higher Ambly-
poda (Fig. 66) and Artiodactyla, and in some of the Perissodac-
tyla (Menodontide, Fig. 81), as well as in the Edentata. In the
three groups first named, this loss has been accompanied by
the development of horny processes on the skull, and this
modification, occurring on three so diverse groups of Ungulata,
excites the suspicion that there is some necessary connection
between the two phenomena. I have suggested that the atrophy
of the incisors in these cases was due to the abstraction of
growth energy and material, from the premaxillary region, for
use in horn-building. But there is no demonstration as yet
attainable that such is a dynamic law. The loss of the incisors

224 COPE. [VoLt. III.

in the wart hog and in the lower jaw of elephants may be asso-
ciated with the great development of the canine and molar
teeth in the former, and of the superior incisors in the latter.
This can be only regarded as a surmise in the present state of
knowledge. In bats loss of median incisors may be ascribed
to disuse, as they certainly can have had, for a long time, very
little functional value. Of the loss of incisors it can be only
said that it is most easily accounted for by disuse, sinée the
molars are naturally preferred for mastication of the soft vege-
table food on which those animals live, owing to their enclosed
position in the mouth. But why the Edentata should have lost
inferior incisors, while Artiodactyla retained them, is not clear,
excepting in the case of genera like Diadomus with approxima-
ted canines.

3. DEVELOPMENT OF MOLARS.

In fishes and reptiles where teeth occasionally present very
primitive conditions, the theory of the origin of particular types
of molar teeth is more simple than in the case of Mammalia.
Under Rule II. direct pressure on a simple tooth crown would,
if long continued, cause it to expand laterally, or in the direction
of least resistance, and to grow but little in its vertical axis, ze.
in the direction of greatest resistance. Constant use will
account for the increased size of such teeth as compared with
those in other parts of the jaws.

In the case of the Mammalia, molar teeth are not traceable
back to ancestral types of reptilian molars, but to simple conic
(haplodont) reptilian teeth. The process of the evolution of the
complex mammalian molars from these, forms the subject of the
following pages.

I have already shown that the greater number of the types of
this series have derived the characters of their molar teeth from
the stages of the following succession. First a simple cone or
reptilian crown, alternating with that of the other jaw (haplo-
dont type). Second, a cone with lateral denticles (the tricono-
dont type). Third, the denticles to the inner or outer side of
the crown, forming a three-sided prism, with tritubercular apex,
which alternates with that of the opposite jaw (tritubercular
type). Fourth, development of a heel projecting from the pos-

No. 2.] THE HARD PARTS OF THE MAMMALIA. 225

terior base of the lower jaw, which meets the crown of the supe-
rior, forming a tuberculo-sectorial inferior molar. From this
stage the carnivorous and sectorial dentition is derived, the
tritubercular type being retained. Fifth, the development of a
posterior inner cusp of the superior molar and the elevation of
the heel of the inferior molar, with the loss of the anterior inner
cusp. Thus the molars become quadritubercular, and opposite.
This is the type of many of the Taxeopoda, including the Quad-
rumana and Insectivora as well as the inferior Diplarthra. The
higher Taxeopoda (Hyracoidea) and Diplarthra, add various
complexities. Thus the tubercles become flattened and then
concave, so as to form V’s in the section produced by wearing ;
or they are joined by cross-folds, forming various patterns. In
the Proboscidia the latter become multiplied so as to produce
numerous cross-crests.

The dentition of some of the Sirenia is like that of some of
the Ungulata, especially of the suilline group, while in others
the teeth consist of cylinders. In the Cetacea the molars of the
oldest (Eocene and Miocene) types are but two-rooted and com-
pressed, having much the form of the premolars of other Mam-
malia. In existing forms a few have simple conical teeth, while
in a considerable number teeth are entirely wanting.

Of the two types of Monotremata, the Tachyglossidz and the
Ornithorhynchide, the known genera of the former possess no
teeth, and the known genus of the latter possesses only a single
corneous epidermic grinder in each jaw. As the Theromorphous
reptiles from which these are descended have well-developed
teeth, their condition is evidently one of degeneration, and we
can look for well-toothed forms of Monotremata in the beds of
the Triassic and Jurassic periods. Perhaps some such (the
Multituberculata) are already known from jaws and teeth. In
the marsupial order we have a great range of dental structure,
which almost epitomizes that of the Monodelph orders. The
dentition of the carnivorous forms is creodont ; that of the kan-
garoos is perissodactyle, and that of the wombats is rodent.
Other forms repeat the Insectivora. I consider the placental
series especially, as the evolution has been similar in both cases.

In ascertaining the mechanical causes of these types of teeth,
the first essential is to ascertain the character of their move-
ments. The following table gives a summary of them :—

226 COPE. [Vot. III.

I. Inferior molars work within superior molars, but not between them.
Psalidodect mastication.
1. The inferior molars shear on the interior side of the superior. Tricono-
dontide.
II. Part or all of inferior molars work between superior molars. Amce-
bodect mastication.
2. The inferior molar shears forwards on the superior molar. Proterotome

mastication . é : . Creodonta; Carnivora.
3. The inferior molars chest pasteriony against the superior Beene Opis-
thotome mastication : : . Coryphodontide, Uintatheriide.

III. Molar teeth of both jaws oppose each other. Antiodect mastication.

4. The movement of the lower jaw is vertical. Orthal mastication ;
Suoidea, Tapiride.
5. The movement of the lower wee is from without inwards. Ectal mastica-

tion . : : . many Perissodactyla.
6. The movement of aes jower jaw is porn within outwards. Ental mastica-
tion . A . most Artiodactyla; some Perissodactyla.

Vie The movement of the lowers jaw is from before backwards. Proal;
most Bonewaa:
8. The movement of the lower jaw is from behind forwards. Palinal ;
Proboscidia (Ryder).

The methods of mastication of Division I. may be also defined
by the terms of Division II. Thus the proterotomes are all
orthal, and the opisthotomes are ectal. Some of the orthals are
opisthotome, as the Tapiridez.

4. ORIGIN OF THE TRICONODONT MOLAR.

The triconodont molar is the earliest example of a process
which has been frequent in the history of the Mammalia, viz. :
the appearance.of cusps or folds at the base of the crown of the
tooth. It is, in the case of the early Jurassic Mammalia which
exhibit it, the Triconodontidz, intimately connected with the
final distinction of the roots of the molars. The ancestors of
this family are probably the Dromotheriidz of the Trias, in
which the separation of the roots is only indicated by a groove,!
a state of things already observed in a species of the Permian
genus of Reptilia, Dimetrodon (Cope). The three or four small
denticles of Dromotherium, are replaced by one in front of and
one behind the principal cusp, in Triconodon. No mechanical
cause can be assigned for the development of these cusps, but

1 See Osborn, American Naturalist, Dec., 1888.

No.2.] THE HARD PARTS OF THE MAMMALIA. 227

the nutrition of the parts probably has had an important influ-
ence on the process. Each basal cusplet stands nearer to the
point of entrance to the crown of the nutritive artery which
ascends — or descends through the root —than any other cusp-
let, and would therefore grow more rapidly than any other
secondary part of the crown under the stimulus of use. The
basal cusplets have thus replaced those occupying more elevated
positions on the principal cusp, and ultimately in some groups
equal it in dimensions; as in the true inferior sectorial of Car-
nivora, and in quadritubercular types.

5. THE ORIGIN OF THE TRITUBERCULAR MOLAR.

The anterior cusplet of the triconodont crown has been called
in the upper jaw the paracone, and in the lower jaw the para-
conid ; and the posterior cusplet is the metacone or metaconid,
respectively. These cusplets serve to fill up the spaces between
the teeth, and thus to produce a certain amount of interference

Figure 51.— Tricondon ferox Marsh, inner side of ramus; three times natural
size: g, mylohyoid groove.

figure 52.— Menacodon rarus Marsh: a, outer, c, inner, side of ramus, three
times nat. size; all from Jurassic beds of Wyoming; from Marsh.

228 COPE. . L VoL. TLE:

between those of opposite jaws. As the lesser cusps are the
less resistant to the wedging pressure of such contact, their
position would change under its influence, rather than the large
central cusps. The lower jaw fitting within the upper, the effect
of the collision between the cusplets would be to emphasize the
relation still more ; that is, the cusplets of the upper jaw would
be wedged outwards, while those of the lower jaw would be
pressed inwards, the major cusps retaining at first their original
alternate position. With increase of the size of the teeth the
cusps would soon assume in each jaw a position more or less
transverse to that of the other jaw, producing, as a result of the
crowding, a crown with a triangular section in both. The pro-
cess may be rendered clear by the following diagram :

ae eee ve Ned

A B G;

Figure 53.— Diagrammatic representations of horizontal sections of tricuspidate

molars of both jaws in mutual relation; the shaded ones represent those of the upper
jaw: Fig. 4, Triconodon; Fig. 2, Menacodon; Fig. C, ideal tritubercular molars,
approached by Menacodon, Fig. 52.

The first modification of the tritubercular molar of the lower
jaw is the addition of a low cingulum at the posterior base.
This is seen in a rudimentary condition in various living species
of the Centetidz and Chrysochloridide of the Insectivorous |
order (Fig. 56); but in these existing forms the superior molar
has added a posterior cingulum also, which widens internally, or
towards the palate (Fig. 54). In the evolution of the dentition,
the inferior posterior cingulum, or “heel,” was developed first,
as in the Deltatherium, Centetes, and Stypolophus (Figs. 54, 56,
58), where it is quite large; while the superior cingulum is want-
ing in Stypolophus and Didelphodus, but is present in a very
rudimentary condition in Deltatherium fundaminis. In all of
these genera the external cusps of the superior series have been
pressed inwards, and more or less together, and are therefore
removed in this respect from the primitive condition. The more
primitive state of the superior cusps is seen in some species of
Miocleenus, where, however, the posterior cingulum is devel-
oped. The primitive type of tritubercular superior molar is that
of Sarcothraustes, and in the same genus the inferior molar only

No. 2.] THE HARD :-PARTS OF THE MAMMALIA. 229

differs from the primitive type in having a well-developed heel.
Among recent Mammalia the carnivorous and insectivorous
Marsupialia generally have the tritubercular lower molar with
heel. In the Chiroptera and many Insectivora the heel is largely
developed, and supports two cusps, as it does in some Creodonta.

Figure 54.— Deltatherium fundaminis Cope, fragmentary skull; two-thirds
nat. size; from the Puerco bed of New Mexico. Figs. a, 4, ¢ from one individual;
Fig. d, from a second animal; Fig. a, right side of cranium; 4, palate from below;
c, mandible, part from above; 4d, left ramus, outer side; from the Report of the U.S.
Geol. Surv. Terrs., Vol. III.

From this point the evolution of the tritubercular molar must
be considered from two standpoints. The first is the mechani-
cal cause of the changes of its form; and the second is the
mechanical cause of its definite location in a particular part of
the jaw. For it has been already stated that in the evolution of
the sectorial dentition of the Carnivora, the number of molars
and premolars has considerably diminished.

In the tritubercular dentition the crowns proper of one jaw
alternate with those of the other (Fig. 56); but when heels are
added in either jaw, they will oppose such part of the crowns of

230 COPE. (Vou. IIE.

the teeth in the opposite jaw as comes in contact with them
when in use. The development of the heel in the inferior
molars produced a type which is known as the tuberculosecto-
rial. This type characterizes the Creodonta and a few Carnivora.
In the former there are generally three such teeth, in the latter
but one.

Figure 55.— Molars of Triassic and Jurassic Mammalia, enlarged; from Osborn:
z, Dromotherium; 2, Microconodon; 3, Amphilestes; 4, Phascolotherium; 5, Tri-
conodon; 6, Peralestes; 7, Spalacotherium; 8, Amphitherium; g, Peramus; zo, As-
thenodon; zz, Dryolestes; 72, 73, Amblotherium; 74, Achyrodon; 75, Kurtodon;
all inferior molars except Figs. 5, 6, and 15.

6. ORIGIN OF THE TUBERCULOSECTORIAL MOLAR.

In this type of inferior molar the primitive tritubercular part of
the crown stands principally anterior to the posterior root of the
tooth. It appears that the posterior root has been extended back-
wards, so as to occupy a position below the middle of the superior
molar, while the tritubercular crown has been confined to the
space between the crowns of the superior molars. This would
follow of necessity from the alternating action of the crowns of
the opposite series, in connection with a general increase in

No. 2.] THE HARD PARTS OF THE MAMMALIA. 231

size of the teeth. In the opening of the jaws in a Creodont,
the elevated portion of the inferior crown shears by its posterior
face against the anterior face of the superior molar, thus re-

Figure 56.— Centetes ecaudatus: A, skull, side seen obliquely from below; A;
superior molars from below; C, inferior molars from above.

straining its extension posteriorly. The stimulus of use, how-
ever, develops a low extension posteriorly, or a heel, which cov-
ers the posterior root, and opposes in mastication the internal
extremity or tubercle of the crown of the superior molar above it.
Thus a molar element in mastication is added to the sectorial in
some Creodonta, and in Canidz and Urside, etc., among Car-
nivora. This function predominates over that of the anterior
triangle in the Lemuridz (Fig. 57).

ZT

eZ

Y ff
U) ;

i Hi Mi (

Figure 57.— Lemur collaris, dentition closed, showing development of heel of
inferior molars; original.

222 COPE. [Vot. III.

7. ORIGIN OF THE SECTORIAL DENTITION.

The successive modifications of form which have resulted in
the existing specialized single inferior sectorial tooth of the
Felidae have been already pointed out. They have been shown
to consist in the gradual obliteration of the internal and poste-
rior tubercles, and the enlargement of the two external tubercles
of the primitive triangle, together with the extinction of the
heel. The modification in the character of the dentition taken
as a whole was shown to consist in the reduction of the num-
ber of the teeth, including the sectorials, until in Felis, etc., we
have almost the entire function of the molar series confined ©
to a single large sectorial in each jaw.

The genesis of the superior sectorial tooth has been explained
as follows. In consequence of the fact that the lower canine
tooth shuts anterior to the superior canine, the result of the
enlargement of the diameters of those teeth will be to cause
the crowns of the inferior teeth to be drawn from behind for-
wards against those of the superior teeth (Fig. 58). Thus a
shearing motion would result between the anterior external edge
of the lower triangle and the posterior internal edge of the

Figure 58.— Stypolophus whitie Cope; diagram representing the apposition of
the inferior and superior molars. The superior are in light, the inferior in heavy
lines. The numbers represent the molars and premolars: C. canine; foc. proto-
cone; fac. paracone; mc.metacone; POC. protoconid; PAC. paraconid; A/C. meta-
conid; 4c. hypocone; A/C. hypoconid.

superior triangle. Now the characters of the true sectorial teeth
consist in the enormous extension of these same edges in a fore
and aft direction, the inferior shutting inside of the superior.
To account for the development of these blades we must under-
stand that the oblique pressure of the front edge of the lower
tooth, on the hind edge of the superior tooth, has been continued

No. 2. ] THE HARD PARTS OF THE MAMMALIA. 233

for a very long time. We must then observe that the internal
tubercle of the superior triangle has been pushed continually
forwards and been reduced to a very small size. Why should
this occur? Why should not the corresponding tubercles of the
inner side of the lower crown have been pushed backwards,
since action and reaction are equal? The reason is clear: The
superior tubercle is supported by but one root, while the resist-
ant portion of the inferior crown is supported by two, thus
offering twice the resistance to the pressure that the superior
does. But why should the anterior part of the inferior tooth
move forwards? even if it be in the direction of least resist-
ance? This is due to the
regular increase in size of
the teeth themselves, an in-
crease which can be traced
from the beginning to the
end) of the ‘series: “And
this increase is the usual
result of use (Fig. 60).

whe mechanics of” the
above proposition I believe =
to be correct, but I have Figure 59.— Cynodictis getsmarianus Cope;
had occasion to modify the skull one-half natural size: a, right side; 4, left
statement as to the initia-
tory cause of the process. In many primitive Ungulata the
canines have been as well developed as in the Carnivora, yet
the forward pressure of the inferior molars on the superiors has
not resulted, or has not been sufficient to produce sectorial
molars in those types. In the Amblypoda, the lower molars
even shear backwards on the upper ones. It seems then that
this growth of the canines is not in all instances sufficient to
cause a proterotome mastication. I suspect that the more usual
cause is to be found in the voluntary effort of the primitive
flesh-eater, to masticate flesh by the manipulation of his lower
jaw and the body to be divided. The looseness of articulation
in primitive Creodonta will permit a manipulation such as we
observe in various Ungulates to-day. The formation of a habit
of a proterotome mastication would result, and the structural re-
sults would succeed as above pointed out.

The excess of the forwards pressure of the inferior teeth

side from below.

234 COPE, (Vou. ITI.

against the superior over any backwards pressure, has left the
posterior internal cusp of the triangle of the inferior molar with-
out contact or consequent functional use. It has, consequently,
gradually disappeared, having become small in the highest Cani-
de, and wanting in some Mustelidz, and all Felidz. The
heel of the same tooth has had a similar history. With the
diminution in size of the first superior tubercular, with which it

Figure 60.— Aelurodon savus Leidy; diagram representing coadaptation of
crowns of superior and inferior molars in mastication; lines and lettering as in Fig. 58.

comes in opposition in mastication, its functional stimulus also
diminished ; and it disappeared sometimes a little sooner (Feli-
dz) and sometimes.a little later (Hyaenidze) than that tooth.

The specialization of one tooth to the exclusion of others as
a sectorial, appears to be due to the following causes. It is to
be observed in the first place that when a carnivore devours a
carcass, it cuts off masses with its sectorials, using them as
shears. In so doing it brings the part to be divided to the angle
or canthus of the soft walls of the mouth, which is at the front
of the masseter muscle. At this point the greatest amount of
force is gained, since the weight is thus brought, immediately
to the power, which would not be the case were the sectorial
situated much in front of the masseter. On the other hand, the
sectorial could not be situated farther back, since it would then
be inaccessible to a carcass or mass too large to be taken into
the mouth.

The position of the sectorial tooth being thus shown to be
dependent on that of the masseter muscle, it remains to ascer-
tain a probable cause for the relation of the latter to the dental
series in modern Carnivora. Why, for instance, were not the
last molars modified into sectorial teeth in these animals, as in
the extinct Hyzenodon, and various Creodonta. The answer ob-
viously is to be found in the development of the prehensile char-
acter of the canine teeth. It is probable that the gape of the

No. 2. ] THE HARD PARTS OF THE MAMMALIA. 235

mouth in the Hyznodons was very wide, since the masseter was
situated relatively far posteriorly. In such an animal the ante-
rior parts of the jaws with the canines had little prehensile
power, as their form and anterior direction also indicates. They
doubtless snapped rather than lacerated their enemies. The

same habit is seen in
the existing dogs,
whose long jaws do
not permit the lacera-
ting power of the ca-
nines of the Felidz,

though more effective

in this respect than
those of the Hyzno-
dons. The usefulness

of a lever of the third
kind depends on the

approximation of the
power to the weight ;
that is, in the present
case, the more ante-
rior the position of
the masseter muscle,
the more effective the
canine teeth. Hence
it appears that the re-
lation of this muscle
to the inferior dental
series depended origi-

Figure 61.— Smilodon neogeus Yund; skull right side; from the Pampean epoch

of Buenos Ayres; original; much reduced.

nally on the use of the canines as prehensile and lacerating
organs, and that its relative insertion has advanced from behind
forwards in the history of carnivorous types. Thus it is that
the only accessible molars, the fourth above and the fifth

236 DORE. [ VoL. III.

=

below, have become specialized as sectorials, while the fifth,
sixth, and seventh have, firstly, remained tubercular as in the
dogs, or, secondly, have been lost, as in hyzenas and cats. .

The reduction of the number of molars in relation to the in-
crease in the size of the canines commenced as early as the
Jurassic period.t It is seen in the genera Triconodon (Owen)
and Paurodon (Marsh), where the canines are large and the molars
few. In the Plagiaulacidz a similar relation is seen between
the development of the incisors and the reduction in number of
the molars. This is the modification of relation observed in ex-
isting Mammalia of the orders Proboscidia and Rodentia, which
will be mentioned later, under the head of proal dentition.

8. ORIGIN OF THE AMBLYPODOUS DENTITION.

As the Amblypoda form the only order of ungulate Mammalia
with tritubercular superior and tuberculosectorial inferior mo-
lars, the question has arisen in my mind why they did not develop
a sectorial dentition in the same way, and for the same mechan-
ical reasons, that the unguiculate series has done so. Having
assigned certain mechanical reasons for the evolution of the
sectorial teeth of the Carnivora, it is necessary to explain why
the Amblypoda, which had apparently the same mechanical con-
ditions at the start, did not eventually produce the same result.

In the first place I observe in the families Coryphodontide
and Uintatheriide of the Amblypoda, that the shearing of the
inferior molar crests against the superior molar crests, is from
before backwards. In the Creodonta and Carnivora it is from
behind forwards. I supposed the latter movement to be due in
these animals to the wedging of the inferior canine in front of
the superior canine, a movement undoubtedly sufficient to ac-
count for such a shearing, other things being equal. But in the
Coryphodontidz the canines are greatly developed, yet the shear-
ing of: the molar crests is in the opposite direction. It is also
evident that the development of the canines cannot have been
the cause of the maintenance of any kind of a shear between
alternating parts of molar teeth, otherwise the quadritubercular

1 My attention has been called to this point by my friend, Prof. H. F. Osborn, who
has recently written fully on the Mesozoic mammals, and whose nomenclature of the
dental cusps is here adopted.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 237

type of molar would not have come into existence in such fami-
lies as have large canine teeth, such as the Suoid Artiodactyla.
I do not for these reasons abandon the opinion that the develop-
ment of the canines has not had a great deal to do with the
development of the sectorial dentition. I only deny that it has
been the cause of its origin; that is, of the anterior shearing of
the lower molars on the upper, at its beginning.

The peculiarities of the Pantodont and Dinoceratous denti-
tion may be now taken up in order, and their mechanical causes
assigned so far as possible. J imine I take the position that
the mastication of the Amblypoda was accomplished by the
transverse movement of the lower jaw across the upper, and
that this is, therefore, the only order in which such mastication
was preformed by the primitive dentition, z.e. the tritubercular
and tuberculosectorial. That this is the type of mastication is
suggested, but not proven, by the anisognathism of the dental
system. But it is proven by the mark or path made by the pos-
terior external cusp of the inferior true molar across the crown
of the superior molar in the Coryphodontidz. This cusp struck
the posterior side of the rudimental anterior external lobe, and
passed transversely across the crown (diagonally to the principal
cross-crests), and slid up the apex of the internal cusp, producing
the externally di- SG {as a
rected angle in its EEE aoe
wear, seen in all spe-
cimens of the gen-
era Metalophodon,
Coryphodon, and
Ectacodon (Fig. 63).
I also suspect that
this movement is
ectal, since the di-

rection of the V’s of ;
the two dental series Figure 62,— Bones and teeth of Pantolambda bath-
modon Cope, two-thirds nat. size. From the Puerco
beds of New Mexico. Fig. a, part of maxillary and
An attempt at an jnalar bones from below, showing true molars, all some-
ental movement re- what broken. Figs. 4 and ¢, cervical vertebree, left side;
sults in a jamming WY andc, do. from below. Fig. d, astragalus from above;

f the V’s into each d', from front, showing facet for cuboid; d_ ,from below;
3 e, navicular bone from below. Original, from Report

other, and further U.S, Geol, Surv, Terrs., F, V. Hayden.

will permit no other.

238 COPE. (Vor. III.

progress is impossible. It may be objected that the presence
of the large superior canines forbids any considerable lateral
movement of the lower jaw. The superior canines are, however,
so divergent in the Coryphodontidz that such movement is
possible, and the transversely convex wear of these teeth proves
just such a movement of the inferior canines on them. The
lateral movement in the old males of the Dinocerata has been
much restricted by the superior canines, but in younger males
and females it was possible.

A second proposition is demonstrated by the discovery of
the Pantolambididz. This is, that the superior molars of both
the Coryphodontide and Uintatheriidz are derived from a type
with two external V’s (Pantolambda, Fig. 62), and I propose to
show how this derivation has been accomplished, and under
what mechanical necessity. Pantolambda also shows that the

Figure 63.— Superior molar series of Coryphodontidze, two-thirds nat. size; from
the Wasatch beds of Wyoming; original. Fig. a, Ectacodon cinctus Cope. Fig. 4,
Metalophodon testis Cope.

inferior molar structure of the two types mentioned has been

produced by the modifications of a W-shaped type of crown. I

note in passing, that the type of Pantolambda is itself readily
3 — tubercular

derived from the primitive 2———— type of primitive pla-
5 — tubercular

centals and marsupials.
With these propositions established, I proceed to consider

No. 2.] THE HARD PARTS (OF THE MAMMALIA. 239

first the origin of the dental peculiarities of the Corypho-
dontidee.

First, no posterior inner tubercle was developed on the supe-
rior molars. We may regard this as a consequence of the fact
that a transverse (ectal) movement of the lower jaw was estab-
lished before the appearance of this cusp, instead of after it, as
was the case in other ungulate orders, and because the shearing
has been always from before backwards, instead of overlapping
from behind forwards, as in all other Ungulata. The stimulus
already assigned as the cause of the development of the fourth
tubercle is, under these circumstances, wanting (Fig. 64).

Second, the anterior cingulum, which extends from the inter-
nal cusp to the anterior external angle of the crown along its
anterior base, is greatly developed. This may be reasonably
ascribed to the stimulus produced by the friction of the poste-

figure 64.— Mutual relation of inferior and superior molars of a Coryphodont
Amblypod. Relations and letters as in Fig. 58. The superior series is that of the
Ectacodon cinctus Cope; the inferior, that of Bathmodon radians (supposed); hence
the anterior V of the inferior premolars is too far anterior.

rior limb of the anterior V of the inferior molar in the trans-
verse movement in mastication. The anterior crest of the
superior molar is developed instead of the corresponding poste-
rior crest of the superior molar in front of it, because the trans-
verse movement of the inferior molar follows a path much more
nearly coinciding with the anterior crest of the superior molar
than with the posterior crest. That is, it follows a curved path
of which the centre is posterior, and near or between the glen-
oid cavities on which the mandibular rami move, as has been
described by Ryder in various other Ungulates.! This is the
probable cause of the development of this crest from its origi-

1 Proceedings Philadelphia Academy, 1878, p. 56.

240 COPE. [Vot. III.

nally moderate proportions in Pantolambda (Fig. 62), and from
the unknown ancestor of that genus, where its dimensions are
presumably still less considerable.

Third, the anterior external tubercle or V is reduced to a coni-
cal rudiment (Fig. 63 a). This is evidently due to the disuse fol-
lowing the great development of the anterior cingulum which
extends from the internal tubercle to the anterior external angle
of the crown. A similar but less considerable development of
this ridge is accompanied by a corresponding reduction of the
anterior external lobe, in some genera of the Lophiodontid
Perissodactyla. The reason why this V has been extinguished
and not merely pressed backwards, is the fact that the posterior
external V of the superior molar has retained its place, and has
not given away to allow room for the anterior one. This V has
retained its place partly on account of its remoteness from the
source of pressure in front, but principally because it fits the pos-
terior transverse crest of the lower molar in front, and the an-
terior oblique crest of the next succeeding lower molar behind,
so that its use has been only possible in its primitive position.

Fourth, the posterior limb of the posterior external V of the
superior molar is wanting on the last molar in Coryphodon, and
from the last two in Metalophodon (Fig. 63). The absence of
this crest from the last superior molar is due to the absence of a
corresponding crest of the inferior molar (Fig. 64). This is the
oblique crest at the anterior extremity of the inferior molar, and
it shears against the posterior limb of the posterior external V
of the superior molar, representing the sectorial blade of Car-
nivora. It is little elevated in the Coryphodontidz, owing to
the fact that it is little used, since the crests of the inferior
molars shear backwards and not forwards on those of the upper.
The effect of this disuse tends, in the history of the Corypho-
dontidz, to become more and more evident. The non-existence
of a fourth molar behind the third in the lower jaw, accounts
for the absence of the crest in question from the last superior
molar, while the absence of the same crest from the second
superior molar of Metalophodon, indicates the absence or rudi-
mentary condition of the corresponding crest of the correspond-
ing inferior molar (Fig. 65).

The above four propositions cover the principal peculiarities
of the dentition of the Coryphodontide. I now proceed to a
consideration of those of the Uintatheriidz.

No.2.] THE HARD PARTS OF THE MAMMALIA. 241

As is well known, the crowns of the superior molars in this
family support two cross-crests, which converge and nearly join
at the internal extremity of the crown (Fig. 66). The anterior
of these crests is pretty clearly the anterior cingular crest of

Figure 65.— Coryphodon latidens Cope, lower jaw, one-third nat. size; from the
Wasatch epoch of New Mexico. Fig. a, right ramus from internal side. Fig. 4, both
rami from above. Original, from Report U. S. G. G. Surveys W. of tooth Mer.,
G. M. Wheeler in charge. This specimen has an anomalous premolar.

Coryphodon, but the homology of the posterior crest is less

obvious. In order to determine this point, recourse must be

had to the inferior molars, which are more readily understood.
In the lower molar of the Uintatheriidze, we find the anterior

242 COPE: [Vor TH:

triangle of the tuberculo-sectorial type, but with the anterior
limb rudimental. The posterior part of the crown differs from
that of the Coryphodontide in having no posterior transverse
crest, but in its stead the diagonal crest which connects the
external extremity of the posterior transverse with the interior
extremity of the anterior transverse crest. This oblique crest
wears the posterior crest of the superior molars on its anterior
face, as the anterior transverse
crest wears the anterior crest (cin-
gular) of the superior molar on its
anterior face (Fig. 67).

Comparison with the dental
structure of Pantolambda (Fig.
62) shows which crests of the
two series stand in this relation to
each other. The diagonal crest
of the inferior molar in this genus
shears in front of the posterior limb

Figure 66. — Dinocerata, teeth, of the anterior V of the superior
bre tous nat. ee Upper. HULGS molar. Guided by this fact we
superior molars of Uintatherium Let- ;
dianum, one-fourth nat. size. Lower may regard the posterior Cross-
figure, inferior molars of jaw of an- crest of the superior molar of the
other species of Uintatherium. From Ujntatheriide, as the posterior
1 ah all and Jimb of the anterior external V.

We must then suppose that the
anterior limb of this V has disappeared from this type of
molar, and the anterior cingular crest has taken its place, thus
forming a long V with the posterior limb. The tubercle
between the crests at their open external valley, may be a
remnant of this external crest. A low tubercle on the crown
behind the inner extremity of the posterior crest may be a
rudimental fourth tubercle (hypocone), or even the apex of the
posterior external V.

The homology of the posterior crest of the superior molar
here proposed, is sustained by the fact that there is no posterior
transverse crest on the lower molar.!_ Had the crest in ques-
tion been part of the posterior V of the superior molar, the pos-
terior crest of the inferior molar would have had use, and would
not have disappeared.

1 The raised heel on these inferior molars is not the posterior transverse crest.

No. 2. ] THE HARD PARTS OF THE MAMMALIA. 243

If this homology is correct, the Dinocerata were derived
directly from the Pantolambdidz, and not through the Corypho-
dontidz.

The mechanical causes of the peculiarities of the Dinocera-
tous dentitions are then the following : —

First, development of anterior cingular crest ; cause same as
in Coryphodontide.

Second, loss of anterior limb of anterior external V of superior
molars ; cause, disuse.

Third, shearing of oblique crest of inferior molar in front of
instead of behind posterior limb of anterior external V of supe-
rior molar. Cause, development of anterior basal cingulum of
superior molar, which wedges cross-crests of inferior molar ante-
riorly.

Figure 67, — Uintatherium, mandible anterior to coronoid process, one-fourth nat.
size; from Bridger beds of Wyoming. From Osborn, memoir on Loxolophodon and
Uintatherium.

Fourth, loss of posterior cross-crests of inferior molars. The
answer to this question is the answer to the other question,
Why was the oblique crest of the inferior molar developed in
the Uintatheriidz while it remained rudimental in the Corypho-
dontidz ? The answer to these questions is the explanation of
the principal peculiarities of the former family. The answer
appears to me to be simply that while the movement of the
lower jaw in mastication was probably ectal in the Coryphodon-
tide, it was probably ental in Uintatheriide. This explanation
is largely hypothetical, yet is accords with the relations between
use and the development of the crests in the two families. In
the ectal movement in Pantolambda the oblique crests of the
opposing molars are soon separated from mutual contact, so
that none of them have use on the internal half of the crown

244 COPE. [Vot. III.

except the anterior cingular. In the ental movement, on the
other hand, the limbs of the external V’s are used to the utmost.
The posterior limb of the anterior V is most used in Panto-
lambda, for the reason, as it appears to me, that the inferior
molar is wedged forwards as it moves outwards in consequence
of the guidance of the anterior cingular crest, and the wedge-
shape of the triangular superior molar. While this causes the
greatest use of the posterior limb of the anterior external V, it
withdraws the posterior crest of the inferior molar from shear
with the anterior crest of the posterior V, so that it has disap-
peared through disuse.

In general it may be observed, that the ental movement
is the easier to the Dinocerata because the V’s open exteriorly
in both jaws. In the Pantodonta the ectal movement is eAsier,
because the V’s of the lower molars open interiorly.

9g. THE ORIGIN OF THE QUADRITUBERCULAR MOLAR.

The quadritubercular molar of the upper jaw was produced by
the addition of a tubercle, the hypocone, at the posterior side of
the internal tubercle of the original tritubercular crown. This
appears first as a cingulum in the Condylarthrous family of

Figure 68.— Phenacodus primevus Cope; diagram representing relation of supe-
rior and inferior molars in mastication; lettering as in Fig. 58.

the Periptychidz and the Creodont genus Mioclzenus, as ex-
amples. A cusp rises on the inner part of this cingulum, which
is at first rudimental, as may be seen in M/voclenus corrugatus
and Chriacus truncatus as examples. It acquires in successive
forms increased proportions, as may be seen in the Phenaco-
dontidee (e.g. Phenacodus primevus, Fig. 68). In the inferior
molar the quadritubercular is formed by the loss of the para-
conid, and the development of two hypoconids on the oppo-
site angles of the heel. The paraconid diminishes farz passu
with the increase in size of the superior hypoconid (fourth tub-

No. 2.] THE HARD PARTS OF THE MAMMALIA. 245

ercle), which, when it is developed, opposes the metaconid of
the inferior molar. The metacone of the superior series op-
poses the protoconid of the inferior. Thus, although the teeth
of the superior and inferior series are alternate, they do not
interlock. On the contrary, they oppose each other, forming a
mechanism adapted for the grinding instead of the cutting of
food.

The divergence of mammalian dentition into the two types,
the tritubercular and quadritubercular, has been, as it appears
to me, due to the adoption of different food-habits. The tritu-
bercular is the primitive, and is adapted for softer food, as flesh,
so that primitive placental Mammalia were carnivorous or nearly
so. The mastication of hard food was impossible until the
molars of the two series opposed each other, and this was not
accomplished until the quadritubercular superior molar was pro-
duced. This was accomplished, as I have pointed out, by the
addition of a posterior internal tubercle, and I suspect that the
mechanical cause of its origin was the attempt of the animal in
mastication to crush substances harder than flesh against this
posterior edge of the superior molar, by applying to it the ante-
rior edge of the lower molar. In the devouring of flesh this
movement is not necessary, or only necessary so far as to pro-
duce a shearing movement to cut a resisting ligament or tendon.
The different mechanical movements in the two cases were due
to the manipulation of its lower jaw by the animals, just as we
may see them to-day endeavoring to masticate substances in
accordance with their hardness, form, etc. It would appear in
the case of the tritubercular superior molar, that the impact
during the effort to masticate hard and tough substances, as
vegetable tissues and seeds, has had its usual effect to stimulate
deposit of material. The shearing movement has had an oppo-
site effect, viz.: that of wearing away the surface subjected to
it, and the flattening of the sheared face. That the develop-
ment of the grinding mastication should take place in ungulate
Mammalia is entirely appropriate to the structure of their digits ;
the hoofed structure unfitting them for the seizure of living prey.

The completion of the quadritubercular dentition requires
that the two anterior cusps and two posterior cusps of the infe-
rior molar should reach the same horizontal plane. This in-
volves the lowering of the anterior pair, and the elevation of the

246 COPE. (VoL. III.

posterior. In the species of Mioclanus the relation of the
cusps to the plane may be seen in various stages of transition.
In most of them the first inferior true molar retains more or
less of its elevation, which is due to the fact that the first pre-
molar is always tritubercular, and leaves a triangular space be-
tween it and the first true molar.

Figure 69.— Diagrams showing successive modifications of dentition from the
haplodont (7) to the protodont (2), the triconodont (3), the double tritubercular (4),
the carnivorous tritubercular (5), to the less and more completed quadritubercular
(6,7); from Osborn. The genera represented are: 7, Delphinus; 2, Dromothe-
rium; 3, Triconodon; 4, Peralestes and Spalacotherium; 5, Didymictis; 6, Mio-
clenus; 7, Hyopsodus.

The mechanical cause of this change is to be found in the
relations existing between the opposing molars after the appear-
ance of the hypocone (fourth tubercle) of the superior series.
The effect of the latter when it should impinge on the para-
conid of the inferior molar,
would be to prevent con-
tact of the heel (hypoco-
nid) of the lower molar
with the interior part (pro-
tocone) of the superior mo-

Figure 70. — Relation of the quadritu- lar next posterior to it. The
bercular superior to the quinquetubercular presence of such a slight

amferior EHS in mastication; from Osborn, eap would not interfere with
American Naturalist, December, 1880. Pr. F
the cracking of seeds or

protocone; 7%. protoconid; #y. hypocone;
hy, hypoconid; fa. paracone; fat. para- nuts, but would prevent the

conid; me. metacone;y me’. metaconid; finer mastication of all sub-
en?, entoconid; m/. metaconule; //. para- stances. It is pretty clear
that the mastication would
have to be performed by the anterior part of the inferior molar
on the posterior part of the superior, by a dentition passing from
the tritubercular to the quadritubercular condition. Such use as

conule.

No. 2.] THE HARD PARTS QF THE MAMMALIA. 247

it would get would probably stimulate the posterior part of the
crown (heel) of the inferior molar until it should rise to meet
the internal part of the superior. The more rapid wear of the
paraconid and of the hypocone would bring about the general
contact of the two series of molars in animals of mature age.
The increased development of the heel of the inferior molar
under these circumstances may have brought about the atrophy
of the paraconid by appropriation of material of nutrition. But
this explanation is hypothetical only. At present there is none
other to offer.

10. THE ORIGIN OF THE LOPHODONT MOLARs.

Quadritubercular molars have their tubercles either simple or
modified into crests; to the two conditions have been applied
the terms dunodont and lophodont. The component tubercles,
or crests, of each tooth, may be either opposite to or alternate
with each other; these conditions are termed anztiodont and
amebodont, respectively. Thus all quadritubercular molars
may be classified under four heads, as represented in this dia-
gram :—

Antiodont. Ameebodont.
Bunodont . O33 | Sea pike ne aS as
Lophodont Aa Dat aS, ee

Two principal kinds of relation between the teeth of opposite
jaws also exist, the zsognathus and anisognathus. In the former
the teeth of opposite jaws are of equal width, and the jaws them-
selves oppose each other; in the latter the teeth of the lower
jaw are narrower than those of the upper, and the branches of
the lower jaw embrace a narrower transverse space than the
upper jaws and palate.

The problem presented by the Mammalian quadritubercular
dentition is that of the derivation of the various lophodont or
crested types from the simple and primitive bunodont types.

It is necessary to remember, in the first place, that teeth of
the quadritubercular type no longer alternate with each other
in the vertical direction ; that is, those of the inferior series no
longer occupy the spaces between those of the superior when
the jaws are closed. In the vertical sense they oppose each
other. This has been accomplished by the development of the
fourth tubercle, forming an inner posterior angle of the superior

248 COPE. [Vov. III.

molar, which thus closes the space between its crown and that
of the adjacent superior molar ; and by a corresponding change
in the inferior molar. In this tooth the anterior interior cusp
has disappeared, and the two cusps of the heel have become
elevated, so as to be on a level with the remaining anterior

Figure 71.— Transverse vertical sections of superior molar teeth, showing transi-—
tion from bunodont (7) type to lophodonts (2, 7). Fig. 1, Sas erymanthius. Fig.
2, Ovis amatheus. Fig. 3, Bos taurus. From Ryder, after Gaudry. Letters: @. den-
tine; ¢. enamel; c, cementum.

Figure 72. — Transverse vertical sections of molars of Proboscidia, showing same
transition as in last figure; lettering the same. Fig. 1, Dinotherium giganteum ;
Fig. 2, Mastodon americanus; Fig. 3, Elephas ganesa; Fig. 4, E. planifrons ; Fig.
5, Z. hysudricus ; Fig. 6, 2. indicus.

No.2.] THE HARD PARTS OF THE MAMMALIA. 249

two cusps. The result is an inferior quadritubercular molar,
which opposes the superior molar which chiefly lies above it,
together with a small posterior part of the superior molar in
front of the latter.

It is a fact that the majority of Mammalia with bunodont
dentition (the peccary, man) are also isognathous, while the
majority of the lophodont types are anisognathus (tapir, ox).
Striking exceptions to the latter rule are seen in the Rodentia
and in the elephant. But there is evidently some connection
between anisognathism and the lophodont dentition. Examina-

Figure 73.— Transverse sections through the maxillary apparatus of a, Fiber;
6, Lepus; ¢, Dicotyles; ad, Cervus; e, Equus. Figs. @ and ¢ represent isognathous
dentition, and 4, d, and ¢ anisognathous; from Ryder.

tion shows that the anisognathous lophodonts have a different
articulation of the lower jaw from that of the isognathous lopho-
donts. It is also found that the movement of the lower jaw on
the upper in the bunodonts differs from that which is exhibited
by either of the lophodont types, and that this motion is in some,
but not all cases, rendered necessary by the shape of the articu-
lation of the lower jaw with the skull. The motions of the three
types may be represented as follows :—

BUNOGONE 2 i ius'x AS (Orta perme vent... vertical:
Eophodont,typeone . |. . “(ectallandiental).. . . . transverse.
Lophodont, type two . . . (propalinal). . . . . . anteroposterior.

In the bunodont type the movement of the jaws in mastica-
tion is identical with that belonging to the tritubercular type,
in which no other than the vertical is possible. It is rendered

250 COPE. (VoL. 1H.

necessary in many of the bunodonts by the structure of the
glenoid cavity of the squamosal bone, which grasps the condyle
of the lower jaw in front and behind, forbidding any but a direct
movement. This is the case in the peccary, but it is not found
in the hippopotamus, the Quadrumana, or the Anthropoidea.
In the lophodonts, type one (mostly Ungulata), the mandibular
condyle is not confined in front, and thus it has free lateral
movement. In the second type of lophodonts (Rodentia and
Proboscidia) the condyle is not confined anteriorly or poste-

Figure 74. — Skull articulations of the mandible in a, 4, c, the giraffe; d, e, wild
cat; and f, 9, Hydrocheerus. Figs. @ and f, vertical views; 4, e, and g, profiles; and
c and d, posterior views; from Ryder.

riorly, but is bounded by a lateral longitudinal crest of the
squamosal bone. The movement must be, therefore, fore and
aft, whether the mouth be much opened or not.

We may now examine the cause of the evolution of the lopho-
dont, type one, from the simple bunodont. Both types exist
within the order Diplarthra, and it has been already shown that
the former have descended from the latter in each suborder of
that order.

In the accompanying figure (75) from Ryder the movements
of the lower jaw in mastication of lophodonts, are diagramma-
tically represented. Fig. @ represents the movement in Car-
nivora, and in the orthal bunodonts, as the pigs. Fig. 6 shows
a slight lateral movement believed by Ryder to exist in the
wart hog (Phacochcerus). Fig. ¢c represents the movement in

No. 2.] THE HARD PARTS OF THE MAMMALIA. 251

kangaroos, phalangers, and tapirs. In Fig. da theoretical inter-
mediate movement is represented, such as Ryder supposed to
have characterized the Anchitherium. In e the usual move-
ment among ruminants is depicted, as is seen in the deer, etc.

SUE ge

a Hal \
abe d

f

Figure 75.— Diagram of excursions of lower jaw in mastication; from Ryder.

In f the wider excursion of the jaw is that seen in the giraffe,
camel, and ox. In these movements from @ to f, the lower jaw
is moved transversely across the upper jaw from one side to the
other.t Some of the Diplarthra masticate on one side of the
jaw when performing this movement, and some on the other.
That is, in passing the lower
jaw across the face of the
upper, some masticate the
food on the side where the
external face of the lower
jaw crosses the upper jaw
from within outwards. (en-
tal) ; while in other types the
food is masticated on the side
where the lower jaw passes
the external edge of the up- @*---------..7_MWA
per jaw from without inwards
(ectal). While masticating figure 76. — Cervus, molars: a, superior,
: : ‘ external view; 4, do. inferior view; c, infe-
with one side of the LENS the rior molars, superior view; from Ryder.
opposing dental series of the
other side are not in contact. All mutual effect of the teeth
of one jaw on the other could therefore appear on the side

1 Ryder was at first of the opinion that the grinding process was produced by the
movement from within outwards in all cases; Zc, p.65. He afterwards observed
that the movement was the reverse in the rhinoceros, or from without inwards, and
he then changed his former opinion and regarded the latter movement as universal.
I have shown that both Ryder’s observations are correct, and applicable to different
groups.

252 COPE. IVGLe It.

temporarily used for mastication only. Among recent Ungu-
lata the ruminants present the ental mastication ; the rhinoce-
ros and horses, the ectal ; and rodents and proboscidians, the
proal and palinal respectively.

When the crests of the inferior molars were developed, their
relation to the crests of the superior molars was always anterior
in mastication. That is, the inferior crest, in the closing of the
jaw, collides with the crest of the upper molar, with its posterior
edge against the anterior edge of the latter. This is because:
first, as to position, the two anterior cusps of the lower molar
are the remains of the anterior triangle which fit originally be-

ine
a

v 4 \

Figure 7’7.— Cusps of superior premolars and molars: @, external cusp of molar of
Sarcothraustes; 4, of Phenacodus; c, of Anthracotherium; ¢, of Oreodon; e, half of
inferior molar of Cervus; /, superior premolar of Coryphodon; from Ryder.

tween two superior molars, and because, in the closing of the
jaw, these cusps continue to hold that position ; and second, as
to function, because the canine in the ungulate series diminishes
in size, and does not, therefore, draw the inferior molars forwards
as in the Carnivora, but allows free scope to the posterior trac-
tion of the temporal muscle in its exercise on the lower jaw.

In those forms which masticate from the inside outwards, the
cusps of the inferior molars, passing between those of the supe-
rior molars, would tend to flatten the sides on which they exerted
friction, and to extend those sides outwards beyond the median
apex of the cusp. The result would be, and taking into view the
yielding of the tissue to such strain, has been, to modify the
shape of the cusp by pushing its side walls, so that a horizontal
section of it would become successively more and more cres-
centic. The effect on the inferior teeth would be to produce
the same result in their external cusps, but in the opposite direc-
tion. The sides of the cusps would be pushed inwards, past
the apex, giving a crescentic section more or less perfect, as the
operation of the cause had been of long or short duration. The

No: 22] THE HARD PARTS OF THE MAMMALIA. 253

result of the lateral movement in mastication may be under-
stood by reference to the accompanying cut. The external
crescents (c) of the inferior molars (4) are seen to pass between
the internal crescents (@) of the superior molars (a). The mu-
tual interaction and effect :

on the form of the cres-
cents may be readily un-
derstood. In Fig. 77 the
successive stages of this
effect on one or two cusps
may be seen, beginning
with a cone (a) and termi-

: : Figure 78. — Two true molars of both jaws
nating with crescents of a ruminant: @, superior molars; 4, their inner
(ef). Thus is the origin crescents; 4, inferior molars; c, their external
of the selenodont denti- crescents; ef, directions of motion of jaws in
fioeon thc highest eee mastication; from Ryder.

odactyle explained by Ryder, and, I believe, correctly.

The problem of the origin of the Perissodactyle types of molar
dentition is somewhat different.1. The peculiarity of the supe-
rior molars of Perissodactyla, as compared with Artiodactyla, is
that the interior tubercles are of less elevation and complexity
than the exterior. Of less importance is the fact that in the
majority of forms, in the lower jaw, the internal cusps alternate
‘with the external cusps instead of standing opposite to them as
is the case in Artiodactyla. With the exception of the Tapiridz
and some Lophiodontidz, the Perissodactyle inferior molars are
amoebodont. The two arrangements are produced by different
types of superior molars, but the modifications have been
brought about in the same way in both antiodonts and amcebo-
donts. ,

In the Hyracotheriina, the ancestral type of all Perissodac-
tyla, the mandibular condyles are strongly convex, transversely
as well as anteroposteriorly. The effect of this structure on
mastication is to allow the ramus of the mandible to twist as it
rises at the end of its transverse excursion. In other words, the
contractions of the masseter and temporal muscles throw the

1 Ryder has supposed, after examining the superior molars of Symborodon, that
the modifying force has acted from without inwards, and has applied this view to all
Diplarthra. I believe this to have been impossible, and that his first view is the cor-
rect one,

254 COPE. gore the

inferior molars with especial force against the external edge of
the superior molars in passing or meeting them. In this way
the external cusps in both jaws sustain the greater part of the
strain and friction in mastication. Thus it is, I suspect, that
the external cusps have acquired such pre-eminent dimensions in
this order. They have also sustained the same lateral shearing
from within outwards that the internal crests have experienced
in the selenodont Artiodactyla, and with the same result, their
gradual modification into crescents. The absence of such shear-
ing pressure between the internal cusps has resulted in their
retaining their primitive conical form to a comparatively late
geological age, as is seen in all forms of the order except the
genera Hippotherium and Equus.

The peculiar form of the mandibular condyle of Hyracotherium
is visible in a less degree in Anchitherium and in Symborodon.
It is still less visible in Equus, and is quite wanting in Tapirus
and Rhinocerus. But the latter have retained the dental char-
acter inherited from the Hyracotheriinz.

figure 79. — Hyracotherium venticolum Cope; mutual relations of molars in
mastication. The space bordered by light lines the superior masticating surfaces;
those by heavy lines, the inferior; C, canine. Lettering as in Fig. 58.

It has been already pointed out that three lines of descent
diverge from the Hyracotheriinz, viz.: the Rhinocerotine, the
Tapirine, and the Equine. The origin of the dental peculiar-
ities of these may be now considered.

In the Hyracotheriinz the intermediate tubercles of the supe-
rior molars, derived from the Condylarthra, remain, and assume
an important part in the construction of the crown. In the
Artiodactyla, on the contrary, they disappear. This is possibly
due to the crowding in a transverse direction which the crowns
of the molars experience in that suborder. In the Perissodac-
tyla they may have one of two positions: they are either in the
transverse line with the other cusps, or they alternate with

No. 2. ] THE HARD PARTS OF THE MAMMALIA. 255

them. When they join the internal cusps and form crests, the
latter are either obliquely transverse to the anteroposterior di-
ameter of the crown (most of the genera), or directly trans-
verse (Tapiridze), or longitudinal (Equidz). The causes effecting
these changes may be now considered.

In the Tapiridz the absence of any noteworthy lateral move-
ment of the lower jaw has prevented the development of cres-
cents on the crowns of the molars of either jaw. The fact that
the intermediate tubercles of the upper jaw are opposite the ex-
ternal ones has led to the development of transverse crests in
both jaws. The development of these crests must be regarded
as the result of simple growth, which has pursued the direction
of least resistance. The growth has been stimulated by the
fore-and-aft mutual contact of the tubercules of each set of
teeth on the other.

In the case of the genera with alternate intermediate cusps
in the molars of each jaw, the connecting crests when present
have naturally become oblique. We notice that from the primi-
tive type of Hyracotheriinz, two lines possessing this character
have had their origin: those of the rhinoceroses and those of
the horses, the latter commencing with the Lambdotheriidz. In
the former the external crest of the superior molars do not form
V’s; in the latter they do (Figs. 80, 81). In both, intermediate
tubercles have been developed in lines anterior to the apices of
both the external and internal cusps. It results from this that
when these join the inner tubercles, they form parts of crests
which reach the external wall of the crown anterior to the cor-
responding external cusps.

As the intermediate tubercles alternate with both internal
and external cusps in the upper molar, it follows that the ex-
ternal cusps of the inferior molars in passing from within,
across the superior molars, pass obliquely over the summits of
the former. This draws out the anterior external angle of the
tubercle so as to form its prolongation as a crest, to the notch
between the external cusps, as in Anchitherium (Fig. 83).
When this crest is completed, the posterior oblique branch of
the inferior V in vertical motion shears on its anterior edge as in
other Ungulates, differing only from the tapirs in being oblique
instead of transverse. In transverse horizontal motion, the lower
crest crosses it at an oblique angle. In the Equine series the

256 COPE. [Vou. III.

posterior cingulum of the superior molar suffers attrition from
the anterior crest of the anterior exterior cusp of the inferior
.molar. In Anchitherium this develops a tubercle which be-
comes ultimately a short crest directed outwards and_back-
wards. This forms the third or posterior intermediate tubercle.
It is wanting from the rhinoceros line. The intermediate tu-
bercles, now crests, have the following relations to the external
crests, now V’s, of the inferior molar. The anterior is parallel
to the posterior limb of the anterior V; the median is parallel
to the posterior of the second V; the third is parallel to the
anterior limb of the anterior V. The posterior forms, then, with
the anterior of the tooth following it, an incomplete V, with its
apex external, and therefore corresponding in direction and posi-
tion to the anterior V of the inferior molar. The second in-
ferior V is only met by a representative of its posterior branch
in the upper molar. But a crest of the upper molar correspond-
ing to its anterior branch develops later in the germs Anchip-
pus. This branch first appears as a process from the median
intermediate crest (Fig. 82, zap) extending anteriorly towards
the anterior intermediate. In Anchippus the posterior and
median intermediate tubercles unite and form a crescent oppo-
site to the external, and connected with the posterior internal
tubercle. In Hippotherium the anterior branch of the median
joins the posterior interior extremity of the anterior median,
thus forming another intermediate crescent opposite the ante-
rior external. These intermediate crescents have exactly the
same mechanical relation to the inferior crescents that the ex:
ternal superiors have ; they alternate with them, and their horns
cross obliquely in lateral mastication. We have here another
illustration of the law that the horus of molar crescents are pro-
longed in the direction of thrust by the corresponding parts of the
opposing molar. The interior tubercles remain small in the
horse line for the reason already given, —their little use. The
only exception to this rule appears at the end of the series,
where in the genus Equus the anterior internal cusp becomes
enlarged like the others.

In the rhinoceros line, where the posterior intermediate does
not appear, the anterior intermediate falls into line with the
transverse crest, and remains so. The median intermediate, on
the other hand, develops an imperfect crescentic form in the

No. 2.] THE HARD PARTS OF THE MAMMALIA. 257

true genus Rhinocerus, after passing through intermediate
stages. In the first of these it extends in a nearly straight line
anteriorly, as in Aphelops, etc. In later genera its extremity
joins a short internal process of the external wall, ¢,g. in Rhi-
nocerus, but it is evident that the crescent thus formed has not
the character of that which is developed in the genus Equus.
The essential peculiarity of the superior molars of the Rhi-
nocerontine line is, that the external wall of the crown does
not develop V’s. This peculiarity is seen in some of the Lophio-
dontine ancestry, especially in the genus Hyrachyus (Leidy).
Ryder has already shown that in Rhinocerus the mastication is °
ectal, but he did not apply this fact to the explanation of the

figure 80.— Hyrachyus agrestis Leidy, superior molar teeth (ectal type) from
below; Eocene of Wyoming; from Leidy.

absence of V’s in the superior molars in this line. I suspect
that the ectal mastication commenced in some of the Lophio-
dontide. The appearance of the anterior external cusp in
Lophiodon and Hyrachyus renders this probable. In these gen-
era the anteroposterior edges of that cusp are drawn zzwards,
as would result from the ectal mastication, and not outwards, as
results from the ental (Fig. 80). It presents a narrow V, with
the apex outwards. The posterior part of the external wall of
the molar is, however, somewhat flexed inwards, and in some
types gives the appearance of an open V directed in the oppo-
site direction from the anterior V. This at once suggests
ental mastication, and introduces the question whether the ex-
planation offered for the origin of the anterior V is correct.
Examination shows that this posterior V is not entirely homol-
ogous with the’ posterior V of the ental dentition, but is ho-
mologous with the entering angle between the external cusps,
directed inwards instead of outwards. This is confirmed by the
fact that its apex, in the Eocene genera mentioned, the point

258 COPE. [Vou. III.

of junction of the oblique transverse crest with the external wall,
looks zzwards instead of outwards; the true second external
cusp is behind this point, as is the first external cusp in the
same crown. In the inward movement of the inferior molar
crown over the external wall of the superior molar in mastica-
tion, the shearing and pressure are of course effected by the
posterior faces of the transverse crests of the inferior molars
against the anterior faces of the corresponding crests of the
superior molar. In crossing the external wall of the superior
molar, the shearing is on that part which is opposite to the
‘transverse crest, and from before backwards. The crests of the
superior molars which are immediately posterior to a transverse
crest receive no, or relatively little, shearing strain. The result
is that the part of the wall in front of the posterior external
crest and cusp is carried inwards by the ectal movement of the
posterior crest of the inferior molar, while the crest behind that
cusp, being without such strain, remains either in line with the
anterior wall ridge, or remaining in its original position poste-
riorly, is carried inwards with the anterior crest and cusp, thus
forming an open V._ It is also probable that in this line there
has been in mastication a rotary movement of the inferior mo-
lars on the superior. The ectal has evidently been a backward
movement as well; if so, the ental movement would be a for-
ward one. Such a movement would at once account for the
outward flexure of the posterior free extremity of the external
wall of the superior molar (Fig. 80) ; since it would in that case
receive the outward shear of the anterior part of the inferior
molar behind and below it. The same movement would account
for the external extension of the anterior cingulum of the
superior molars, which is such a characteristic peculiarity of the
Lophiodontidz and of their Rhinocerontine descendants.

The inferior molars of the Perissodactyla develop from the
primitive quadritubercular type in two directions, the one anti-
odont, the other amcebodont, as already stated. In the former
the cusps unite to form cross-crests; in the other the junction
of the cusps forms a W or double crescentic pattern. We have
the former in some members of the Lophiodontidz, in the
Tapiride, and in the Rhinocerontine series generally. The
latter type is characteristic of the Equine series.

The origin of the crests is, in accordance with I. (p. 218), sim-

No. 2.] THE HARD PARTS OF THE MAMMALIA. 259

ple growth, resulting from use, in the direction of least resistance.
Hence in teeth with opposite cusps, growth will connect them if
anywhere, thus avoiding collisions with the corresponding growth
in the opposite jaw. This is the primitive relation of cusps, and

‘paonpar yonur {[eursi10 fopesojoD Jo paq JOA azY AA

wo {soovjans Sueoyseu ‘uoyUap saoisayut pue solsadns ‘adod swcaz0uostg woposoguds — ‘1g IANSUT

its result. In some of the Lophiodontidz (e.g. Systemodon) a
slight alternation is observable in the cusps of the inferior
molars, while those of the superior molar remain opposite. This
alternation is developed to its fullest extent in Anchitherium,
where the external and internal cusps of the superior molars are

260 COPE. [Vot. Ii.

still opposite. This peculiarity of the inferior molars is due
to the development of intermediate tubercles in the superior
molars, in front of the line which could connect the external
and internal cusps, as has been already described. These
appear in a rudimentary condition in Hyracotherium, and pre-
sent an increasing development in all the lines of the suborder.

The mechanical effect produced by them on the opposing
(inferior) molar teeth is as follows. An external cusp of the
inferior molar in passing across the face of the superior molar
(ental) is deflected forwards so soon as it strikes the intermediate

Figure 82.— Protapirus priscus Filhol, superior and inferior molar teeth, grinding
faces; from the Eocene phosphorites of Quercy; from Filhol.

tubercle. In this position its apex is nearly opposite to the cor-
responding external and internal cusps of the superior molar.
As the inferior molar is narrower than the superior, its interior
cusps become engaged with those of the superior molar, as the
external cusps of the former reach the intermediate cusps of
the latter. Now were the internal cusps of inferior molar
directly opposite to the external cusps of the same, the former
would in these circumstances come into collision with the in-
ternal cusps of the upper series. In order to pass through
the intervals of the internal cusps of the superior molars, the
internal cusps of the inferior molars must alternate with the
exterior cusps of the same. They have been forced into this
position by the constant pressure on and by the internal cusps
of the superior molar, which they engage on the posterior side,
and not on the anterior side, as is the case in types where the
intermediate tubercles are either in transverse line with the

No. 2.]

THE HARD PARTS OF THE MAMMALIA.

261

others, or are wanting. The development of V’s from these
alternating cusps has then proceeded as in other types, with

the exception peculiar to the Peris-
sodactyla already referred to, that
the external cusps only in both jaws
are thus developed (Fig. 83).

II. ORIGIN OF THE PROAL DENTI-

TIONS.

A. Rodentia. The phylogeny of
the Rodentia as an order is now
tolerably clear. I at first suggested,}
and later asserted? that this order
was derived by descent from the
Tillodont suborder of the Bunothe-
ria. The Tillodont suborder had a
common origin with the Tzenio-
donta, from some type of Bunothe-
ria with unspecialized molars and
premolars, in which some of the
incisor teeth had begun to display
enlarged size. A form allied to
this ancestor is the genus Estho-
nyx, which differs from it in but
few respects. Professor Ryder, in
discussing the origin of the Roden-
tia,?> writes as follows: “The sig-
nificance of accessory rudimentary
incisors present in some forms of
true rodents, as pointing to the man-
ner in which the evolution of the
rodent type of dentition took place,
may be overrated; yet when it is
borne in mind that in other groups
the appearance of diastemata be-

Figure 83.— Anchitherium equi-
ceps Cope; superior and inferior
molars in apposition, showing rela-
tions of crests at different stages
of mastication; one-half larger
than nat. size; original. A, The
last inferior molar beginning its
transit across the superior molar, at
the inner margin. 4, The inter-
nal cusps of the former between
those of the latter. C, The inter-
nal of the inferior between the ex-
ternal of the superior.

tween the different kinds of teeth took place gradually, and in

1 American Naturalist, April, 1883; report U.S. Geol. Surv. Tertiary Vertebrata,

1885, p. 814.
2 Loc. cit., April, 1884,

3 Proceedings Academy Philadelphia, 1877, p. 317.

262 COPE: (Vor. HI.

a way which unmistakably shows the gradual steps of the process,
we may be excused for thinking the same to have been the case
here, although without positive tangible evidence in the shape
of intermediate fossil forms that exhibit such a passage from
the ordinary type.”
In 1882 I had the
pleasure of discover-
ing a genus! (Psitta-
cotherium Cope),
which supplies the
desideratum wanting
when Professor Ry-
der wrote. This isa
genus without dias-
tema, and with two
effective rodent-like

Figure 84.— Psittacotherium multifragum Cope, incisors in each ra-
left mandibular ramus; one-half nat. size; original; mus of the lower jaw.

from Puerco bed of New Mexico. Fig. a, external Ectoganus Cope is
5

probably similar in
these respects, but
only its separate teeth
have been found.
Psittacotherium is
then a_ generalized
type and is not far
from if not directly in
the line of the ances-
try of all Rodentia.
It belongs to the Pu-
erco fauna, which
embraced so many of
the progenitors of la-
ter Mammalia (Fig.

84).

view; 2, superior view.

Figure 85. — Calamodon simplex Cope, lowe jaw, I have called atten-
left ramus; one-third nat. size; original; from Wasatch |. Raa h
Eocene of Wyoming. Fig. @, external view; 4, supe- tion to the tact that
rior; cd, inferior molar; ¢, exterior, d, posterior views. the first inferior inci-

1 4merican Naturalist, February 1882. Tertiary Vertebrata, 1885, p. 195.

No. 2.] THE HARD PARTS OF THE MAMMALIA. 263

sor is rudimental in Calamodon, and Marsh has shown the same
thing in Tillotherium. In both genera the second incisor is the
effective tooth. The third is apparently present in Calamodon
(Fig. 84), but the homology of this third tooth is not yet fixed. In
Tillotherium the third incisor is apparently wanting. In Psittaco-
therium the first incisor tooth is present and effective, but the
second is larger. It is not certain whether these are first and
second, or second and third incisors. If we allow Esthonyx
to decide the question, the large second tooth is truly the
second incisor, for in that genus the first incisor is small, and
the third is rudimental. With present information, then, the
inferior incisor of the Rodentia is the second of the Mammalian
series, !

The peculiarities of the rodent dentition consist, as is well
known, in the great development of the incisors; the loss of all
but one, or rarely of two, of the premolars, which leave a wide
diastema; and the posterior position of the molar teeth, as relates
to the rest of the skull. A peculiarity which belongs to the
highest types of the order is the prismatic form of the molars,
and the deep inflection of their always transverse enamel folds
both laterally and vertically. A peculiarity of the masticating
apparatus, which is the basis of distinction from the Bunotherian
order, is the lack of postglenoid process, and the consequent
freedom of the lower jaw to slide backwards and forwards in
mastication. Appropriately to this motion the condyle of the
mandible is either subglobular, or is extended anteroposteriorly,
and the glenoid cavity is a longitudinal instead of a transverse
groove.

The mechanical action of the development of the rodent
dentition has been as follows. The first factor in the order of
time and importance was the increasing length of the incisor
teeth. Those of the lower jaw closed behind those of the upper
in the progenitors of the Rodentia (e.g. Esthonyx) as in other
Mammalia. Increase of length of these teeth in both jaws

1] have regarded (Naturalist, 1884, April and earlier) the Tzeniodonta as the
ancestors of the Edentata. The objection to this view is the supposed absence of in-
ferior incisors in the latter. But the middle incisors have disappeared from some of the
Tzniodonta, while the supposed canines of the lower jaw of Megalonyx and allies may
be true incisors. This is rendered probable by the genus Diadomus of Ameghino,
where the large canine-like teeth are close together at the symphysis mandibuli, like
the incisors of the Tzeniodonta and Rodentia,

264 COPE. [Vo. III.

would tend to keep the mouth permanently open, were it not
for the possibility of slipping the lower jaw backwards as it
closed on the upper. This backward pressure had undoubtedly
existed, and has operated from the earliest beginning of the
growth of the rodent incisors. The process has been precisely
the opposite of that which has occurred to the Carnivora, where
the pressure has been ever forwards owing to the development
of the canines.t The progressive lengthening of the incisors
through use has been dwelt on by Professor Ryder (4c.). The

Figure 86.— Castoroides ohioensis Foster, skull, right side; two-fifths nat. size.
Fig. a, inferior insertion of masseter muscle; @, fossa inside of ascending ramus;
c, external auditory meatus; d, incisors; e, foramen infraorbitale; from Hall and
Wyman.

posterior pressure on the lower jaw produced by its closing on
the upper, has been increased directly as the increase in the
length of the incisors, especially those of the lower jaw.

The first effect of this posterior pressure will have been to
slide the condyle of the mandible posteriorly over the post-
glenoid process, if any were present, as is probable, in the
Bunotherian ancestor of the rodent. Continued repetition of
the movement would probably push the process backwards so
as to render it ineffective as a line of resistance, and ultimately

No. 2.] THE HARD PARTS OF THE MAMMALIA. 265

to flatten it out against the otic bulla, and atrophy it. The
lower jaw would thus come to occupy that peculiarly posterior
position which it does in all rodents.

The anteroposterior (proal!) type of mastication becoming
necessary, an appropriate development of the muscles moving
the lower jaw, with their insertions, follows, pavz passu. As
a result we see that the insertion of the temporal muscle creeps
forward on the ramus, until in the highest rodents (Cavia) it
extends along the ramus to opposite the first true molars. The
office of this muscle is to draw the ramus backwards and up-
wards, a movement which is commenced so soon as the inferior
incisor strikes the apex of the superior incisor on the posterior
side. By this muscle the inferior molars are drawn posteriorly
and in close apposition to the superior molars. Connected with
this movement, probably as an effect, we find the coronoid
process of the mandible to have become gradually reduced in
size to complete disappearance in some of the genera, e.g. of
Leporidz. In these genera the groove-like insertion of the
temporal muscle develops as the coronoid process disappears.

As third and fourth effects of the posterior position of the
lower jaw, we have the development of the internal pterygoid
and masseter muscles and their insertions and origins. The
angle of the ramus being forced backwards, these muscles are
gradually stretched backwards at their insertions, and their con-
traction becomes more anteroposterior in direction than before.
The internal pterygoid becomes especially developed, and its
point of origin, the pterygoid fossa, becomes much enlarged.
The border of the angle of the mandible becomes more or less
inflected. In their effect on the movements of the ramus they
oppose that of the temporal muscle, since they draw the ramus
forwards. They are the effective muscles in the use of the
incisor teeth; that is, in the opposition of the inferior incisors
against the superior from below and posteriorly. Hence the
great development of the internal pterygoid and, in a less degree,
of the masseter. Both muscles tend also to close the jaws, but
at a different point in the act of mastication from that at which
the temporal acts. If we suppose the mouth to be open, the
action of the masseter and internal pterygoid muscles draws the
mandible forwards and upwards until the incisors have performed

1 See page 226 for explanation of the different modes of mastication.

266 COPE. [Vou. III.

their office, or the molars are in contact with each other or with
the food. They then relax, and their temporal muscle continues
the upward press-
ure, but draws the
ramus backwards
to the limit set by
the adjacent parts,
causing the act of
mastication.

AA mith eect ‘ot
the development
of the incisors and
of the proal mas-
tication, is seen in
the position of the
molar teeth. The
indefinitely repeat-
ed strain and press-
ure applied to the
superior molars
from forwards and
below has evident-
ly caused a gradual
extension of the
maxillary bone
backwards, so that
pterygoid fossa; c, internal pterygoid plates; d, fossa in the last molars oc-

basioccipital bone; ¢, external auditory meatus; f, mastoid CUupy a position
process; g, occipital condyles; 4, tympania bulla; after much posterior to

Hall*and Wyman. fiat baintek they
do in other orders of Mammals. This is especially the case in
such forms as Bathyergus, Arvicola, and Castoroides (Fig. 86),
where the last molars are below the temporal fossa, and poste-
rior to the orbit.

A sixth effect of the causes mentioned has been referred to
by Ryder! This is the oblique direction of the axes of the
molar teeth. These directions are opposite in the two jaws;
upwards and forwards for the lower, and downwards and _ back-
wards for the upper. The mechanics of this change of direction

Figure 87. — Castoroides ohioensis Foster; two-fifths
nat. size; skull from below. Fig. a, incisine foramen; 4,

1 Proceedings Academy Philadelphia, p. 66, Figs. 8, 6 and /-

No.2.] THE HARD PARTS OF THE MAMMALIA. 267

from vertical in the primitive forms (Sciuridze) to oblique in the
genera with prismatic molars, is simple enough. The inferior
crowns when closely appressed to the superior, and drawn _pos-
teriorly in the direction of the long axis of the jaw, press and
strain the teeth in the two directions mentioned. The develop-
ment of the long prismatic crowns which has proceeded under
these circumstances, has been undoubtedly affected by the
pressure and strain, and the direction we find has been the
result.

Figure 88. — Ischyromys typus Leidy, from the White River beds of Colorado;
original; from the Report U. S. Geol. Surv. Terrs.: @, 6, ¢, cranium; d, mandible
from above.

The seventh effect is in the detailed structure of the teeth
themselves. Beginning with short crowns with simple trans-
verse crests (Psittacotherium and Sciuride, Figs. 84, 88), we
reach through intermediate forms, crowns with vertical laminze
of enamel, which sometimes divide the crown entirely across
(Chinchillidze, Caviidae, Castoroididae) or appear only on the side
of the crown, through the continued coalescence of the prisms
of which each molar crown is composed (Arvicola). In many
instances the crowns increase in transverse at the expense of

268 COPE. [Vot. III.

their longitudinal diameter (Castor, Lepus). The vertically

laminated structure is evidently due to the crowding together of
ae

transverse crests by the same pressure
which has given the crowns their oblique
direction. In many genera the length-
ening of the crown has included the
lengthening of the longitudinal connec-
tion between the transverse crests, as
in Arvicola, Castor, and Hystricidze
generally. In others this connection
has not been continued, so that the
“ crown is composed of prisms which are
separate to near the base, as in Am-
“4 blyrhiza and Saccomyide. In others,
/ connection between the prisms has been
/ lost by coenogeny, as in Chinchillidze
| and Caviide generally. The latter fam-
(ilies display also the greatest amount
Figure 89.— Teeth of Hy- of crowding (Fig. 89).

Mihi oe pas ee. A peculiarity of the plication of ro-
after Leidy: @, fragment of Gent molars I am unable to explain as
superior incisor; 4,the shaded yet on mechanical principles. In ge-
portions represent parts of in- nera which are isognathous, the inflec-

ferior molars found. . : :
tions are of equal depth on opposite sides
of both superior and inferior molars. In anisognathous genera
the inflections are more numerous and profound on opposite
sides of the molars of the respective jaws. Anisognathism in
rodents is generally as shown by Ryder, of the type where the

Figure go.— Molars of Rodentia compared with the haplodont (@) and seleno-
dont (@) dentitions: a, Arvicola, first inferior molars; 6, do. profile; e, Thomomys
crowns; /, do, profile; from Ryder.

No.2.] THE HARD PARTS OF THE MAMMALIA. 269

inferior molars include a wider expanse than the superior, though
this applies in some instances more to the direction of the roots
rather than the position of the crowns. In Lepus the lower
jaw is the narrower. I have termed the two types of anisog-
nathism hypanisognathism (Lepus, Diplarthra) and epanisog-
nathism (Caviide). The following genera display these char-
aetehst

Hypanisognathous. Lsognathous. Epantsognathous.
Lepus. Arvicola. Hystricide.
Capromys. Castor.
Caviide.

In conclusion I will say that it is satisfactorily proven to my
mind that nearly all of the peculiarities of the rodent dental
system and manner of mastication, are the mechanical conse-
quences of an increase in the length of the incisor teeth. And
the increase of the length of these teeth has been due to their
continued use, as believed by Ryder.

b. Monotremata Multituberculata. The structure of the
dentition of this suborder is in many respects like that of
the Rodentia in the known forms. The incisors in the Plagi-
aulacidze, Chirogidze, and Polymastodontidz have structure and
functions generally sim-
ilar to those of the Ro-
dentia. The result in
the form and function of
the molar dentition has
been similar to that ob-
served in the Rodentia.

The postglenoid process BS
is probably absent in —< 333 :

these animals; in any
case the mandibular Figure g1.— Chirox plicatus Cope, palate and

condyle is rounded, and molar teeth from below; three-halves nat. size;
Ter at Gian erse Prof from Puerco bed of New Mexico; from American
i ; :

Naturalist, 1887, p. 566.
Pye .Oshborn,) ‘has
pointed out to me that mastication was performed by a fore-
and-aft movement of the inferior molars on the superior in
Plagiaulacidz. This was no doubt the case in the other families
named. The resulting structure of the crown is, however, dif-
ferent, and needs explanation. The molar teeth present conical

270 COPE.

[VoL. III.

Figure 92.— Polymastodon tatensis Cope, jaws two-thirds nat. size; from Puerco
bed of New Mexico. Figs. a, d, lower jaw; ¢, upper jaw; original.

Figure 93. — Monotremata Multitubercu-

lata. Fig. a, Ctenacodon serratus Marsh;
three times nat. size; from Marsh: d, 7,
Meniscoéssus conguistus Cope, three halves
nat. size: d, superior molar; ¢7, humeral con-
dyles; #4? premolar. Fig. 6, Stereognathus
obliticus Owen; three times nat. size; from
Owen; c, Tritylodon longevus Owen; three
times nat. size; from Owen.

tubercles in longitudinal se-
ries, two in the lower and
three in the upper jaw. The
two series of the lower jaw
alternate with the three in the
upper jaw, moving in the
grooves between the latter,
while the three series of the
upper molars reciprocally em-
brace the two of the lower
molars. This is demonstrated
by the mutual wear of the
tubercles seen in Ptilodus
and ‘(Chiroxm (Pic: *o1) “he
trituration was probably the
same in Tritylodon, but in
Polymastodon the increased
thickening of the tubercles
prevented their interlocking
action in mastication. In this

No. 2.] THE HARD PARTS OF THE MAMMALIA. 27%

genus the tubercles slid over each other, and truncated the
apices until in old specimens they were entirely worn away
(Fig. 92, c,¢). In Meniscoessus and Stereognathus we have an
interesting illustration of the effect of the action of cusps on
each other when under prolonged mutual lateral thrust. Their
external sides have been drawn out into long angles in the
direction of thrust, converting their transverse sections from
circles to crescents. As the thrust is in the Multituberculata
longitudinal, the crescents are transverse to the axis of the jaw.
In the selenodont Diplarthra, where the thrust is transverse to
the line of the jaw, the crescents are longitudinal. That similar
effects should accompany similar movements in two groups of
Mammalia so widely separated as these two is strong evidence
in favor of the belief that the two facts stand in the relation of
cause and effect (Fig. 93, Figs. 4 and 2).

IV: CONCLUSIONS.

Summarizing the preceding investigations, the structure of
the Mammalian skeleton and dentition may be referred broadly
to the two general classes: excess of growth, and defect of
growth. Each of these may be again divided into two series,
as follows :—

Excess of growth, oes
) Luxuriance.
Disuse.

Defect of growth, Poveree

Progressive evolution results principally from the first two
conditions, which have frequently codperated in the develop-
ment of structures. These may be classified as effects of the
following mechanical causes : —

A. Motion in Articulation.

1. Impact only, or chiefly.
Facetting of distal end of radius in Diplarthra.
Expansion of proximal end of radius in Diplarthra.
External trochlea of metapodials in Diplarthra.

Grooving of distal end of tibia by astragalus.
Grooving of proximal end of astragalus by tibia.

272 COPE. (Vou. IIL.

2. Torsion only.

Alternation of carpal bones in Anthropomorpha.

Rounding of head of radius in Edentata and Anthropomorpha.
Symmetrical flanges of ulnar cotylus in Anthropomorpha.
Unsymmetrical flanges of ulnar cotylus in most Mammalia.
Involution and sculpture of zygapophyses of Diplarthra.

3. Torsion and impact without flexure.

Alternation of carpal and tarsal bones in Ungulata.

4. Torsion, impact and flexure in one plane.

Tongue-and-groove joint in humerus of Diplarthra.

Tongue-and-groove joint in metapodials of all orders.

Tongue-and-groove joint in phalanges of Edentata, Insectivora,
etc.

5. Flexure in two planes.

Saddle-shaped cervical vertebrze in Quadrumana.

6. Flexure in several directions.

Ball-and-socket vertebral articulations.
Head of humerus.
Head of femur.

AA. Motion not in Articulation (Teeth).
7. Displacement by crowding.

Tritubercular molars.

8. Transverse thrust.

The V’s in molars of both jaws in various orders.

9g. Longitudinal thrust.

The V’s in the molar teeth of the Multituberculata.
Obliquity of molars in many Rodentia.

10. Stimulation of pressure and strain.

Prismatic molars of Diplarthra, Rodentia, etc.
Sectorial teeth of Carnivora,

No. 2.] THE HARD PARTS OF THE MAMMALIA. 273

Confluence of cusps into crests generally.

Canine teeth in general.

Incisors of Rodentia, Multituberculata, etc.
Incisors of Proboscidia, of Monodon, Halicore, etc.

The relation of stimulus to nutrition is as yet so little under-
stood, that there is plausible ground for the assertion that the
hypothesis that use develops structure is “not proven.” What
evidence there is, however, mostly supports the hypothesis,
but the proof of the theory of kinetogenesis (¢.e. the origin
and development of structure through motion) is not in the
least indefinite or inconclusive. I point especially to the his-
tory of the articulations, as described in the preceding pages.
And the general principles which we derive from the investi-
gation are applicable to the entire animal kingdom.

The general law which we may derive from the preceding
evidence is, that in biological growth, as in ordinary mechanics,
Identical causes produce tdentical results. The evidence may be
arranged under two heads, viz. : —

I. The same structure appears in distinct phyla which are
subjected to the same mechanical conditions. Examples: the
identical character of the articulations of the limbs in Diplarthra
and Rodentia which possess powers of rapid locomotion. The
identical structure of the head of the radius in Edentata and
Quadrumana which possess the power of supination of the manus.
Identical reduction of the number of the digits under increased
use of the limbs in many of the orders. Identical modifications
of the form and development of the crests of the skull under
identical conditions of use of the canine teeth for defence in all
the orders where the latter are developed. Identical modifica-
tion of dental cusps into longitudinal V’s and crescents under
transverse thrusts in several orders, and into transverse cres-
cents under longitudinal thrusts in Multituberculata.

II. Different structures appear in different parts of the skele-
ton of the same individual animal, in direct correspondence
with the different mechanical conditions to which these parts
have been subjected. Examples: the diverse modifications of
the articulations of the limbs in consequence of the uses to
which they have been put, in mammals which excavate the
earth with one pair of limbs only; as in the fossorial Edentata,

274 : COPE. (Vo. III.

<

Insectivora, and Rodentia. The reduction of the number of the
digits in the posterior limb only when this is extensively used
for rapid progression, as in leaping: this is seen in the kan-
garoo and jerboas, in the orders Marsupialia and Rodentia.!

There are a good many structures in the skeleton of the
Mammalia which have not yet received a satisfactory expla-
nation on the ground of mechanical necessity. Such, for in-
stance, appears to me to be the history of the origin of the
canine tooth; that is, its use in preference to an incisor for
raptorial purposes. Such may be also the history of the origin
of the complex vertebral articulations of the American Edentata
as compared with the simple articulations of those of the Old
World. In these as in similar cases, however, an element enters
which must be taken into account in seeking for explanations ;
that is, that every evolution is determined at its inception by
the material or type from which it originates. Thus is explained
the fact that identical uses have not produced identical struc-
tures in the limbs of all aquatic vertebrates. The fin of the fish
is essentially different from the paddle of the Ichthyosaurus or
the whale. The beak of the raptorial bird is different from the
canine tooth of the rapacious mammal. When this principle is
duly considered, many mechanical explanations will become clear
which now seem to be involved in difficulty or mystery.

V.. LITERATURE:

1809. Lamarck, J. B. P. A. Philosophique Zoologique, Chap. VII. ; transla-
tion, American Naturalist, 1888, p. g60.

1865. Spencer, Herbert. Principles of Biology, II., pp. 167 and 195.

1871. Cope, E. D. Proceedings of the American Philosophical Society, p.
259; on the Method of Creation of Organic Types, reprinted in
Origin of the Fittest, 1887, p. 210.

1872. Cope, E. D. Penn Monthly Magazine, on Evolution and its Conse-
quences ; reprint, Origin of the Fittest, 1887, p. 30.

1877. Ryder, J. A. American Naturalist, p. 607, on the Laws of Digital
Reduction.

1877. Ryder, J. A. Proceedings of the Academy of Natural Sciences of
Philadelphia, p. 314; on the Significance of the Diameter of the
Incisors in the Rodents.

1 An able presentation of the facts embraced in this section has been made by
Professor Ryder in the American Naturalist, October, 1887, p. 606.

No. 2z.] THE HARD PARTS OF THE MAMMALTA. 275

1878. Cope, E. D. American Naturalist, January; The Relation of Animal
Motion to Animal Evolution; reprint, Origin of the Fittest, 1887,
P- 350.

1878. Ryder, J. A. Proceedings Academy Natural Sciences, Philadelphia,
p. 45; on the Mechanical Genesis of Tooth-Forms.

1879. Cope, E. D. American Naturalist, March; on the Origin of the
Specialized Teeth of the Carnivora; Origin of the Fittest, 1887,
p- 363.

1881. Cope, E. D. American Naturalist, April and June; on the Origin of
the Foot-Structures of the Ungulates; on the Effect of Impacts and
Strains on the Feet of Mammalia; Origin of the Fittest, 1887,
pp- 368, 373-

1887. Cope, E. D. American Naturalist, pp. 985, 1060; The Perissodactyla.

1888. Cope, E. D. Proceedings of the American Association for the Advance-
ment of Science, p. 254; on the Mechanical Origin of the Sectorial
Teeth of the Carnivora.

1888. Cope, E. D. American Naturalist, p. 3; The Mechanical Causes of
the Origin of the Dentition of the Rodentia.

1888. Cope, E. D. The Mechanical Origin of the Dentition of the Ambly-
poda. Proceedings of the American Philosophical Society, p. 80.

1888. Ryder, J. A. The several functions of the enamel organ in the devel-
opment of the teeth of mammals, and on the inheritance of mutila-
tions. American Naturalist, p. 547.

1889. Cope, E. D. American Naturalist, March; The Artiodactyla. (The
elbow joint; the zygapophyses.)

Vi LIST OF COURS THE LEX.

Fic. 1. Limbs of Phenacodus primevus and Homo sapiens.
Fic. 2. Posterior limbs of Artiodactyla: A, Merycocherus montanus; B, Bos
laurus.

Fic. Tarstus spectrum, posterior limb; from De Blainville.
Fic. 4. Tarsi of bats; from Allen.
Fic. 5. Anterior limb of right whale; from Cuvier.

Fic. 7. Monachus albiventer, fore and hind limbs; original.

Fic. 8. Pantolambda bathmodon, posterior digit; original. Coryphodon elephan-
topus, posterior foot; original. Uzntathertum mirabile, posterior foot; from Marsh.

Fic. 9. Phenacodus primevus, anterior foot; original.

Fic. 10. Hyracotherium venticolum, anterior foot; original.

Fic. 11. Protohippus sejunctus, posterior foot; original.

Fic. 12. Poébrotherium labiatum, fore and hind feet; original.

Fic. 13. £guus caballus, fore and hind feet; from Cuvier.

Fic. 14. Artiodactyla, fore feet; from Kowalevsky.

Fic. 15. Procyon lotor, three views in locomotion, showing gait; from Allen.

Fic. 16. Ovis (Gazella) dorcas ; from Standard Natural History.

Fic. 17. Botcherus humerosus, distal extremity of radius and humerus, and fore
foot; original,

a
4
5
Fic. 6. Putorius vison, muscles of the posterior leg; original diagram.
7
8

276 COPE. [Vou. III.

Fic. 18. Phenacodus primevus, anterior foot; original. Coryphodon sp., anterior
foot; original. AWyracotherium venticolum, anterior foot; original.

Fic. 19. Smlodon neogeus, skeleton from Buenos Ayres; from Burmeister.

Fic. 20. Hyena striata ; from the Standard Natural History.

Fic. 21. Phenacodus primevus, carpus and tarsus; original.

Fic. 22. Hyracotherium venticolum, posterior foot; original.

Fic. 23. Cervus canadensis, from behind, trotting; from Maybridge.

Fic. 24. Anterior extremity of a bat; from Huxley and Hawkins.

FIG. 25. Bradypus tridactylus, posterior foot; from Cuvier.

Fic. 26. Cholepus hoffmanii, three positions in locomotion; from Allen.

Fic. 27. Coryphodon elephantopus, posterior foot; original.

Fic. 28. Aphelops megalodus, posterior foot; original.

Fic. 29. Amblyctonus sinosus, distal end of tibia; original.

Fic. 30. Oxyena morsitans, distal end of tibia; original.

Fic. 31. Archelurus debilis, distal end of tibia; original.

Fic. 32. Mimravus gomphodus, femur; original.

Fic. 33. Poébrotherium labiatum, hind foot; original.

Fic. 34. Protohippus sejunctus, hind foot; original.

Fic. 35. Cosoryx furcatus, posterior cannon bone; original.

Fic. 36. Procamelus occidentalis, anterior foot; original.

Fic. 37. Cosoryx furcatus, posterior cannon bone; original.

Fic. 38. Poébrotherium labiatum, anterior foot, part; original.

Fic. 39. Manis indica, fore foot; from Cuvier.

Fic. 40. Priodontes maximus, fore foot; from Cuvier.

Fic. 41. Priodontes maximus, hind foot; original.

Fic. 42. Cervus elaphus, humero-radial, and metacarpo-phalangeal articulations;
original,

FIG. 43. 1, 2, Cosoryx necatus ; 1 without, and 2 with, burr on antler. 3, 4, Coso-
ryx ramosus ; 3, antler broken and reunited, 4, beam with burr; original.

Fic. 44. Cynocephalus, cervical vertebra, three views; original.

Fic. 45. Diagrams representing different types of locomotion, showing motion of
vertebral column in each.

Fic. 46. Cervus canadensis in motion, from behind; showing position of legs in
trot; from Muybridge.

Fic. 47. Mimravus gomphodus, skull; original.

Fic. 48. Lsthonyx burmeistert, dentition; original.

Fic. 49. Psittacotherium multifragum, lower jaw; original.

Fic. 50. Lemur collaris, dentition; original.

Fic. 51. Zriconodon ferox, inferior dentition; from Marsh.

Fic. 52. MJenacodon rarus, inferior dentition; from Marsh,

Fic. 53. Diagrams representing: A, relations of superior and inferior molars of
Triconodon; B, of an intermediate type; C, ditto of Spalacotherium; original.

Fic. 54. Deltatherium fundaminis, cranium and dentition; original.

Fic. 55. Aesozoic Mammalia, molar teeth; from Osborn.

Fic. 56. Centetes ecaudatus, dentition; original.

Fic. 57. Lemur collaris, profile of closed dentition; original.

Fic. 58. Stypolophus whitia, profile of closed dentition; superior molars superposed
on inferiors, the latter in black, the former in double white outlines; original.

Fic. 59. Cynodictis geismarianus, skull one-half natural size; original.

Fic. 60. Aelurodon sevus, superior and inferior molars in relation, diagram; _origi-
nal,

No. 2.]

Fic. 61.

THE HARD PARTS OF THE MAMMALTA.

.

Smilodon neogeus, skull; original.

277

Fic. 62. Pantolambda bathmodon, superior molars, “vertebrze, and bones of hind
foot; original.

Fic. 63.
Fic. 64.
Fic, 65.
Fic. 66.
Fic. 67.
Fic. 68.
Fic, 69.
FIG, 70.
Fic. 71.
FIG. 72.
Fic. 73.
Fic. 74.
FIG. 75.
Fic. 76.
FIG. 77.
Fic. 78.
FIG. 79.
Fic, 80.
Fic. 81.
Fic. 82.
Fic, 83.
Fic. 84.
Fic. 85.
Fic. 86.
Fic. 87.
Fic. 88.
Fic. 89.
FIG. go,
FIG. 91.
FIG. 92.
FIG. 93.

Lctacodon cinctus and Metalophodon testis, superior molars; original.

Molars of Coryphodontide in relation, diagram; original.
Coryphodon latidens, mandible; original.

Uintatherium leidianum, molars; from Osborn.
Uintatherium, lower jaw; from Osborn.

Phenacodus primevus, diagram of molars in relation; original.
Molars of M/ammadiia in functional relation; from Osborn.

Quadritubercular and quinquetubercular molars in relation; from Osborn.

Transverse sections of molars of Artiodactyla ; from Gaudry.
Transverse sections of molars of Prodoscidea ; from Gaudry.
Transverse sections of jaws of Rodentia ; from Ryder.
Posterior parts of lower jaws; from Ryder.

Paths of lower jaws in mastication; from Ryder.

Dentition of Cervus, from Ryder.

Premolar teeth, different types; from Ryder.

Selenodont molars, both jaws, mutual relation; from Ryder.

Lyracotherium venticolum, molars of both jaws, mutual relation; original.

fHyrachyus agrestis, superior molars from below; from Leidy.
Symborodon trigonocerus, molars; original.

Protapirus priscus, molars; from Filhol.

Anchitherium equiceps, molars, mutual relations; original.
Psittacothertum multifragum, lower jaw; original.
Calamodon simplex, lower jaw; original.

Castoroides ohioensis, skull; from Hall and Wyman.
Castoroides ohioensts, skull from below; from Hall and Wyman.
Ischyromys typus Leidy, skull; original.

fydrocherus esopi Leidy, molar tooth; from Leidy.

Molars of Rodentia, Delphinus, and Cervus; from Ryder.
Chirox plicatus, superior molars; original.

Polymastodon tacénsts, molars and lower jaw; original.
Multituberculata, dentition; original,

278

FIc.
Fic.
Fic.
Fic.
Fic,

MUO >

COPE.

EXPLANATION OF PLATE IX.
Elbow joint of Mammalia, dislocated and viewed from behina,

Crocuta maculata.

. Simia nigra.

Rhinolophus.

. Lucrotophus pacificus.

Cervus elaphus.

‘VIIVAWYW 30 SLNIOf MO813

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yaw %, ae
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=

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ee
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NO LI rah

280

COPE.

EXPLANATION OF PLATE X.

Longitudinal sections of limbs, displaying the intimate structure of the articulations.

FIG.
Fic.
FIe.
FIc.
FIe.
FIG.

Ov CRTs CONES

Elephas africanus, distal end of humerus.
Elephas africanus, tibio-astragalar joint.
Elephas africanus, metapodial.

Elephas africanus, metapodial.

Tapirus americanus, anterior leg.

Ovis artes, anterior leg.

Fic, 7, Ovis artes, posterior leg,

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}

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Vol.

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Pl. X.

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282

FIG.
Fic.
Fic.
Fic.
FIG,

pe OSS)

COPE.

EXPLANATION OF PLATE XI.

Vertebra, usually the second lumbar, less than natural size.

Macropus rufus.

Sarcophilus ursinus, enlarged.
Tachyglossus hystrix, enlarged.
Myrmecophaga jubata.
Priodontes maximus,

Plate XI.

\ SAAN
ANY | — SS a HMA
\S™

Wy ———
Uj

VERTEBRA.

284

iG
Fic. 2.
FIG. 3.
FIG. 4.

COPE.

EXPLANATION OF PLATE XII.
Vertebre, asin Plate XJ.

Mesonyx obtusidens, from specimen in Mus., Princeton College,
Canis lupus.

Uncia concolor.
Simia nigra.

Plate XH.

Zz —

VERTEBRZ.

286 COPE.

EXPLANATION OF PLATE XIII.

Vertebre, asin Plate X7/.

Fics, 1-3. Zgews caballus.
Fics. 4-5. Lmpedias phaseolinus, showing hyposphen; a Theromorous reptile
from the Permian formation of Texas.

Plate XTITT.
—.

VERTEBRA.

288 COPE.

EXPLANATION OF PLATE XIV.
Vertebra, as tn Plate XJ.

Fic. 1. Antilocapra americana,
Fic. 2. Dicotyles angulatus.
Fic. 3. Capra hircus.

LETTERING.
ES, Episphen; ZA, epantrum; J//, metapophysis; 72, prezygapophysis; Pz,

postzygapophysis; Zg/, zyganatrapophysis; Df, diapophysis; 47S, hyposphen; dw,
anapophysis; #, humerus; #, ulna; 7, radius.

VERTEBRA.

\ AN \
ws
Wes:

y
ae,
3 8

Plate

XTV.

290 COPE.

CON GENTS:

Preface ;
Introductory enisais on thé phivlaeeny Bi the (tamara
I. The Limbs 5
1. The proportions of the limbs and their aenients
a. Increase of length by impact
B. Increase of length by stretching .
y. Other modifications through use and disuse
2. The number of the digits
3. The fixed articulations
a. The ulna and radius
B. The carpus and tarsus
4. The ginglymoid articulations : :
a. The heads of the humerus and femur .
4. The elbow joint .
c. The femoro-tibial aitictlation
d. The distal hinge of the Artiodactyle sracains
e. The tarsal articulations of the Edentata
jf. The tongue-and-groove joints
II. The Axis of the Skeleton
1. The skull .
a. The sense organs
8. The muscular insertions
y. The horns .
2. The vertebral centra .
a. The articular faces
B. The relative lengths of the verhebue
3. The vertebral arches
4. The scapular arch
5. The pelvic arch .
Ill. The Dentition C 6
1. The origin of the canine ine a
. The development of the incisors
. The development of the molars
. Origin of the triconodont molar
. Origin of the tritubercular molar
. Origin of the tuberculosectorial molar
. Origin of the sectorial dentition
. Origin of the Amblypodous molar
. Origin of the quadritubercular molar
. Origin of the lophodont molars
. Origin of the proal dentitions
a. Rodentia
6. Multituberculata
IV. Conclusions
V. Literature .
VI. List of engravings .

Ley) on Aum fw N

_

THE EMBRYOLOGY OF BLATTA GERMANICA
AND DORVPHORA DECEMLINEATA.

WILLIAM M. WHEELER.

TuE following study of the development of the cockroach and
potato-beetle was taken up during the summer of 1887. On
the suggestion of Dr. W. Patten, without whose stimulating
friendship and assistance the work would not have been under-
taken, I began with A/atta as a form calculated to help me to a
knowledge of the fecundative changes in the Hexapod egg. Dr.
Patten kindly placed at my disposal the results of his own work
on S/atta, in the form of much carefully prepared material and
some figures, which I have incorporated in Plate III. (Figs. 43,
45 to 47, 52).

Later I concentrated my attention on Doryphora, which I
found to be a much more profitable object of study than A/azta,
especially as far as the more advanced stages were concerned.
Thus it happens that my remarks on odgenesis and fecundation
are more complete in 4/a¢ta, while my account of the germ-layers
and subsequent stages is carried into greater detail in Doryphora.

I have seen fit to treat of both insects as nearly as possible
under single headings, instead of describing them independently
in two chapters, because they differ strikingly in all the details
of development, while their main ontogenetic features are as
strikingly similar. By running both descriptions as nearly as
possible in parallel lines, the contrasting details are made more
salient, while the general remarks may be taken up at intervals
and not reserved ev masse till the end of the paper.

PREPARATION.

There are three common species of Blattide in Southeastern
Wisconsin: Periplaneta orientalis (Linn.), Platamodes unicolor
(Scud.), and Alatta germanica (Linn.). The first and the last
occur, as is well known, about houses; the second is abundant
under the bark of decaying logs and stumps in open woods.

292 WHEELER. [Vox. II.

Periplaneta orientalis oviposits from April to August; Blatta
germanica, at all times during the year. The odthece of P/ata-
modes may be collected in great numbers where the insects
abound. After many futile attempts to open the oédthecz of
Periplaneta and Platamodes without injuring the ova, I limited
my study to 4latta, the egg-capsules of which may be easily
opened by the method given below. By careful treatment of
the thick-walled capsules of Periplaneta and Platamodes with a
sufficiently strong solution of sodium hypochlorite, it may be
found possible to isolate the ova in an uninjured condition.

Specimens of Blatta germanica can be obtained at all times
of the year from places which they haunt, and with very little
attention will live long in confinement. The male is long and
narrow, tapering anteriorly and posteriorly ; the female is much
broader and flatter and uses her wings much less than the male.

Males seem to endure the unfavorable condition of captivity
much better than females. When it is desired to time the eggs,
the capsule cannot be detached from the female without damage
till it has been rotated, and during winter must be’ kept under
a bell jar with plenty of moist blotting-paper to prevent the
embryos shrivelling from the dryness of the air.

The ovarian ova in all stages up to maturity were dissected
out in normal salt solution and hardened for fifteen minutes in
Perenyi’s fluid. They were then transferred to 70 per cent
alcohol, which was changed several times at intervals of an hour,
and were finally preserved in alcohol of the same strength.
When stained with borax carmine and sectioned, the yolk retained
none of the red stain, while the chromatin of the nucleus shone
out as a glistening deep red spot. Perenyi’s fluid rendered the
chorion of the mature ovarian egg pervious to borax carmine.

Hardening in a saturated aqueous solution of corrosive subli-
mate gave good results with young ovarian eggs.

Oviposited eggs were killed by placing the capsules in water
slowly heated to 80°-g0°C. The two lips of the crista of the
capsule were then separated by the aid of fine forceps, and pieces
of the walls torn away, till the eggs could be easily pushed out
of the compartments formed by their choria.

The ova thus isolated were either transferred directly through
35 per cent (10 min.) to 70 per cent alcohol, or they were left for
15 minutes in Kleinenberg’s picrosulphuric acid, and after re-

No. 2.] BLATTA AND DORYPHORA. 293

peated washing in 70 per cent alcohol, preserved in alcohol of
the same strength. Both methods gave equally good results.

Though I have succeeded in dissolving the chitin of the
odtheca with sodium hypochlorite, the method of tearing off
the walls after heating to 80°C. gave such satisfactory results
that I adhered to it throughout my work.

I have found Grenacher’s borax carmine in every way the
most expedient and reliable staining fluid. Eggs and embryos
up to the time when the cuticle develops were stained before
imbedding in paraffine; the sections of other embryos were
stained on the slide after attaching them with Mayer’s albumen
fixative.

The clusters of bright yellow eggs of the potato-beetle (Dory-
phora decemlineata, Say) may be found on the under surfaces of
the leaves of the potato-plant during the whole summer, as the
insect is polygoneutic.

The beetles, frequently found copulating, may readily be kept
in confinement, and will deposit their eggs in the typical flat
clusters on the walls of any box or vessel in which they are kept.
As I commenced collecting material late in the season, I did not
keep the insects in confinement till they oviposited, but collected
the eggs from the plant. It was found convenient to cut out
the piece of the leaf to which the egg-cluster was attached and
to keep it by itself during the process of preparation, as all the
eggs of a cluster are in almost exactly the same stage of de-
velopment.

Beautiful results in preparation were obtained by heating the
eggs to 80°C. for 10 minutes in Kleinenberg’s picrosulphuric
acid (with 3 volumes of water) and preserving in 70 per cent
alcohol.

By this process the envelopes, which in the fresh egg adhere
closely to the yolk, dilate and stand off from the surface of the
egg, and except in the very youngest stages can be rapidly and
easily removed with the dissecting needles.

A great number of eggs, heated to 65°C. only, or hardened
in cold Perenyi’s fluid, corrosive sublimate or simple alcohol,
proved to be useless, as the envelopes adhered firmly to the sur-
face of the yolk.

The hot picrosulphuric acid fixes the cells of the embryo in a
most satisfactory manner; enough details of the karyokinetic

204 WHEELER. [Vot. II.

figures being preserved to enable one to recognize dividing nuclei
at a glance. All the eggs were imbedded after treating with
clove oil, in paraffine melting at about 55°C. The somewhat
gummy yolk cut without any tendency to crumble, and perfect
series of sections were obtained without the slightest difficulty.

Staining on the slide with borax carmine gave beautiful results
in all stages, but was resorted to only in young eggs, the vitel-
line membranes of which did not stand off from the surface of
the yolk, and in advanced embryos which had developed the
larval cuticle. To save time, embryos in other stages were
stained before imbedding, after removing the egg-envelopes.
As much as possible of the borax carmine was extracted with
acidulated 35 per cent alcohol.

HISTORICAL.

The cockroaches have long been favorite objects of morpho-
logical study. Easily obtained at all seasons of the year, of
convenient size for dissection, and being but slightly modified
descendants of the oldest insects of geological time, they com-
bine qualifications which make them especially interesting and
valuable to the morphologist. Thus we find that no less than
twenty investigators have sought material for anatomical and
embryological study in the common species of Alattide. I will
mention only those who have treated of the oogenesis and ontog-
eny of Blatta and Periplaneta.

Rathke (42) was the first to publish an account of the devel-
opment of blatta germanica. Brandt (6) made a study of the
ovarioles of Periplancta. UHuxley’s (22) account of the general
anatomy of the same insect contains some valuable remarks on
the ovaries. Kadyi (23) has given us a condensed account of
the oviposition and micropyles of Pevzplaneta orientalis. Patten
(38) in 1884 published a preliminary note on the development
of Llatta. He observed that the first and second maxillz are
at first triramous, and made some remarks on the heart and on
the peculiar organs developed from the appendages of the first
abdominal somite. Stuhlmann (45) treated of the degeneration
of the germinal vesicle in Perzplaneta. During the same year
(1886) also appeared Miall and Denny’s work (82) on the anat-
omy of Periplaneta, containing Nusbaum’s brief embryological

=

No: 2.) BLATTA AND DORYPHORA. 295

description of A/aztta, carelessly written and with figures often
grossly inaccurate.

Blochmann’s important paper (5), announcing the discovery
of polar globules in Alatta germanica and two other insects,
appeared in 1887. The description of the eggs of Blatta is suc-
cinct and perfectly accurate.

Of late, Cholodkowsky (10) has published a preliminary paper
on the formation of the entoderm in Slatta.

Doryphora decemlineata has not been investigated heretofore
from an ontogenetic standpoint. It is surprising that so com-
mon an insect, and one whose eggs present such advantages for
embryological study, should have been overlooked. The favored
Coleopteron of embryologists has always been Hydrophilus, and
it is certain that the water-beetles (Hydrophilide and Dytis-
cide) are much less modified forms than the leaf-beetles (Chry-
somelideé), to which Doryphora belongs.

Nevertheless the development of several Chrysomelids has
been studied more or less incompletely.

Packard (35) made a brief study of Gastrophysa ceruleipennis,
and Melnikow and Kowalevsky (26) studied Donacza.

More exhaustive was the attention bestowed on Lzna by
Graber (15), who published his account in the second volume of
his text-book on insects (1877). As would be expected from
their close systematic affinities, Doryphora and Lina differ but
slightly in their development.

OVARIES AND OVIPOSITION,
PBlatta.

The ovaries of AZ/atta are flattened, broadly spindle-shaped
masses slung in trabecular connective tissue, continuous with
the peritoneum. Each ovary consists of from 14 to 26 ovarioles,
or egg-tubes opening into the oviduct. The latter extends
backwards towards the median longitudinal axis of the body,
and after joining the oviduct from the opposite ovary opens into
the broad and short vagina. Besides the tubular colleterial
glands the vagina carries on its dorsal face near the proximal
ends of the oviduct a thick-walled sac, the spermatheca.

The ovariole has the structure typical in insects. The fol-
licles in all stages of formation are inclosed by the membrana

296 WHEELER. [Vou. III.

propria in the form of a tube tapering to capillary caliber at its
upper extremity, which is attached to the pericardium. The
lumen of the capillary portion is filled with protoplasm in which
numerous small nuclei are imbedded. This portion of the ova-
riole constitutes the germarium. The small nuclei differentiate
at the lower end of the germarium, on the one hand into ova,
which fill the widening lumen of the tube; and on the other,
into flattened epithelial cells, which line the inner surface of the
tube, and form the follicles inclosing the ova. There are about
ten distinct ova in an ovariole, the lowest being the largest, and
the most apical the smallest and most indistinct, those interme-
diate regularly diminishing in size towards the apex. In Perz-
planeta there are about three times as many ova in an ovariole;
but there are only eight ovarioles in an ovary. The lower ova
in both species are oval, and are surrounded on all sides by the
epithelium, which has grown in between the separate eggs to
complete the follicles.

The follicular epithelium (Fig. 5) is composed of large, flat,
polygonal cells, with lenticular nuclei which present an intri-
cately coiled chromatin filament and a nucleolus of unusual struc-
ture. The latter consists of an irregular mass, not stainable in
carmine or methylgreen, and is regarded as plastin by Car-
noy (9), who describes and figures very similar nucleoli in the
egg-follicles of Gryllotalpa. The mass of plastin incloses a
smaller mass of chromatin, or at least of a substance which does
not differ in its reactions from the chromatin of the coiled fila-
ment in the same nuclei. In eggs taken from the ovaries just be-
fore maturity, when the epithelium is still firmly attached to the
underlying chorion, almost all of the nuclei will be found
rapidly dividing. Pieces of the epithelium from eggs of differ-
ent ages were examined in normal salt solution, in methylgreen
acetate held for a moment in the fumes of osmic acid, in Rabl’s
chromformic acid, in Zaccharias’ acetic osmic acid; but no traces
of an achromatic spindle, or of a regular arrangement of the
nuclear filament, so characteristic of karyokinesis could be
observed. I therefore conclude that we have here a case of
akinesis or direct division. This conclusion is further strength-
ened by the observation that the nucleolus divides first (Fig. 5 ¢),
and the nuclear wall is constricted during division, an occur-
rence exceedingly rare in kinetic nuclei, where the nuclear wall

No: 2.] BLATTA AND DORYPHORA. 207

disappears in all but a few of the recorded cases both in plants
and animals. Moreover, the two daughter nuclei are frequently
very unequal in size.

The chorion (Fig. 1) is a thin, chitinous membrane smoothly
covering the surface of the egg. In surface view it appears to
be finely granular, the finest granules being arranged in large,
more or less regularly hexagonal areas, which are bounded by
narrow, dark spaces containing somewhat larger though less
dense granules. Each of the hexagonal areas is secreted by
one of the polygonal epithelial cells described above. It is only
in cross-section that the true structure of the chorion becomes
apparent. According to Blochmann (5),—and my observations
coincide with his, —the chorion consists of two chitinous laminz
kept in close apposition by means of numerous minute trabe-
culz, or pillars. It is the ends of these pillars seen in surface
view that look like granules. In the spaces between the hex-
agonal areas, the trabecule are more scattered and individually
thicker than those of the hexagons. Hence these lines on the
chorion seem covered with larger and more scattered granules.
When pieces of the dry chorion are immersed in glycerine and
immediately examined under the microscope, the thick liquid
may be seen entering the spaces between the hexagonal areas,
passing along them in obedience to the laws of capillarity, and
then slowly creeping from them on both sides into the adjacent
hexagonal areas between their denser trabeculz. I have also
observed that the structure of the chorion of the ripe egg is
most distinct in cross-section at the pole directed towards the
germarium. Here the two lamine seen at vo in Fig. 4 separate
somewhat, and the connecting trabeculae become longer and
more distinct.

I have not been able to trace the formation of the micropyles
in Blatta germanica. Their structure is easily demonstrated.
They are scattered over a quadrant of the upper hemisphere
where the beautiful hexagonal pattern of the chorion gives
away to an even trabeculation (Fig. 2). The micropyles are
wide-mouthed, very oblique, funnel-shaped canals perforating
the chorion (Fig. 2 «2, 0). ) Uhe apertures of the funnels
appear under a low power as clear, oval spots, the long axes of
which are parallel to the long axis of the egg. These perfora-
tions are scattered over the micropylar area, sometimes in clus-

298 WHEELER. [VoL. III.

ters, sometimes singly. With a higher power the tube of each
funnel is clearly visible as a thin canal which dilates rapidly
into the large oval aperture on the outer face of the chorion.
The narrow tube is sometimes fully as long as the large orifice.
The micropylar perforations are all directed from the germa-
rium to the vaginal pole of the egg. Hence a line, the hypo-
thetical path of the spermatozoén, drawn through one of these
oblique micropyles, and continued into the egg, would strike
the equatorial plane. The female pronucleus, as we shall see
further on, moves in this plane.

The micropyles of Per7planeta, first described by Kadyi (23),
do not differ essentially from those of Blatta. In Periplaneta
the hexagonal pattern is continuous over the micropylar area.
The large micropyles, which are more yellowish than the sur-
rounding chorion, are thick walled and not regularly oval, as in
latta, but oblong or subpentagonal. The tube is shorter and
terminates on an hexagonal area. Sometimes the micropyles
are very close together and seem to overlap.

I have repeatedly sought in vain for a vitelline membrane in
the eggs of latta. Blochmann (5) had no better success. It
may exist, but it must be exceedingly thin and inseparably glued
to the inner lamina of the chorion.

The colleterial glands of A/atta are like those which Huxley
(22) and Kadyi (23) have described for Pertp/aneta, a number of
long, blind tubes opening into the vagina. They furnish the ma-
terial for the capsule, viz.: chitin and large crystals of calcium
oxalate. In Alatta these glands are glistening white till the time
of oviposition approaches, when they assume a yellow tint, and
the octahedral crystals are seen imbedded in a viscid sub-
stance which fills their lumina. This viscid substance is sol-
uble in potassium hydrate, and is consequently not chitin.
When excreted to form the odtheca, it slowly hardens, deepens
in color, and becomes insoluble in potassium hydrate. Light
has nothing to do with this change, which is possibly produced
by the oxygen in the air. It is the same change which is
undergone by the cuticula of the insect itself immediately
after ecdysis.

I have made a few observations on the oviposition of Platta
germanica, similar to those published by Kadyi (23) on Pert-
planeta orientalis.

No. 2.] BLATTA AND DORYPHORA. 309.

When about to form the capsule, the female Alatta closes the
genital armature, and the two folds of the white membrane
which lines the odthecal cavity close vertically in the middle
line. Then some of the contents of the colleterial glands are
poured into the chamber and bathe the inner surface of the
posterior wall. The first egg glides down the vagina from
the left ovary, describes an arc, still keeping its germarium pole
uppermost, after having pressed the micropylar area against the
mouth of the spermatheca, passes to the right side of the back
of the chamber, and is placed perpendicularly two-thirds to the
right of the longitudinal axis of the insect’s body. The next
egg comes from the right ovary, describes an arc to the oppo-
site side of the body, decussating with the path of the first egg,
and is placed completely on the left side of the median line.
The third egg comes from the left ovary, and is made to lie
completely on the right side of the median line: and so the
process continues; the ovaries discharging the eggs alternately,
and each egg describing an are to the opposite side of the cap-
sule. In females killed during oviposition each oviduct will be
found distended with eggs, often two or three end to end, in-
creasing the length and breadth of the lumen to an abnormal
degree. Gentle pressure of the female’s abdomen between the
thumb and finger will sometimes cause the insect to oviposit
a few eggs, the paths of which can be seen to decussate.

The o6thecal chamber soon becomes too small to contain all
the constantly accumulating eggs, so the anal armature opens
and allows the end of the capsule to project. A raised line, the
impression of the edges of the white membrane, runs down the
end of the capsule. The last egg deposited comes from the right
ovary and lies two-thirds on the left and one-third to the right
of the median line. Thus the first and last eggs laid lie with
their greater bulk on opposite sides of the median vertical plane
of the capsule, and serve to commence and close the series and
round off both ends of the capsule. Owing to their being
crowded up against the walls of the capsule, they acquire quite
a different shape from the remaining symmetrically and alter-
nately deposited ova. They develop normally, however, the
embryo appearing on the inner obtuse edge. As soon as
the last egg is laid, a further discharge from the colleterial
glands spreads over the vaginal or anterior wall of the cavity,

300 WHEELER. (Vor. IIT.

and becomes evenly continuous with the secretion which has
before been spread over the back and the sides of the capsule by
the white membrane. When the anterior end of the capsule is
examined, the escutcheon-shaped vaginal opening is found to
have left its impression even to the delicate wrinkles into which
the surrounding cuticula was thrown by the closing of the ori-
fice. This end of the capsule is white, gradually shading into
the brown of the opposite end.

The crista, a cord-like ridge running the full length of the
dorsal surface of the capsule, is a thick-walled tube, either half
of which is formed by the edge of the side walls of the capsule
split into two laminz (Fig. 3 04, 0”). The rhythmical clasping of
the three pairs of palpi, which guard the vaginal opening, is
registered in an exquisite pattern on the inner face of either
half of the crista.

The canal is filled with a vacuolated substance (Fig. 3 ef)
which at first sight resembles the yolk of the egg, but when
examined more closely is seen to have quite a different struc-
ture and origin. In the egg ready to leave its follicle the epi-
thelium is much thickened at the germarium pole into a bicon-
vex-lens-shaped cap (Fig. 4), the cells of which are not flat like
those on the other portions of the egg, but long, columnar, and
more or less curved. The two laminze of the chorion spread
apart beneath this cap and dilate into a pear-shaped sac divided
up into numerous polygonal chambers by delicate chitinous
partitions (Fig. 4 4). While the egg is leaving the follicle, the
epithelium at the lower pole is loosened from the chorion, and
the egg protrudes into the oviduct. As it advances, the epithe-
lium is rolled back and doubled up in folds till it is freed from
the chorion as far as the cap. Then it breaks, letting the egg
pass into the oviduct with the thick cap of cells firmly attached.
The egg is-placed in the capsule, and the cap comes to lie in
the crista, filling its lumen. The large nuclei degenerate, and
soon entirely disappear, the protoplasm becomes dry and vacuo-
lated, and finally transformed into the yolk-like mass described
above. This substance probably serves as a cement to keep
the lips of the crista in contact till separated by the emerging
larvee. Thus a small portion of the follicular epithelium, that
portion which corresponds to the nourishing cells in other
insect ovaries, is deposited with the egg. To my knowledge

No. 2.] BLATTA AND DORYPHORA. 301

this has not been observed in any other arthropod eggs hereto-
fore described, excepting Musca (Bruce, 7). The pear-shaped
dilatation of the chorion is directly over the head of the future
embryo and hatching insect, and is possibly more easily rup-
tured or dissolved than the surrounding chorion.

Of 40 capsules examined for the purpose of noting which
ovary sent out the first and which the last egg, 32 com-
menced with the right egg (from the left ovary) and closed
with the left egg (from the right ovary), six capsules commenced
and closed with the right, and one commenced and closed with
the left egg. Evidently the 32 were normal; in the insects
which deposited the six, one of the ovarioles was probably
either atrophied or wanting, though the perfectly alternate
arrangement of the eggs in the capsule was in nowise inter-
rupted on this account. The two remaining egg-capsules were
small and abnormal.

The number of eggs in a capsule, far from being constant in
Periplaneta orientalis, is even more fluctuating in Blatta ger-
manica. In 34 capsules counted the average number was about
40, the least number 28, and the greatest 58. The number
varies in different localities and is doubtless dependent on the
food of the female insect. In several capsules obtained where
amylaceous food was abundant the average was much higher
than in a much greater number of capsules obtained from a
place where fatty food was the only diet.

The above description of the oviposition of Blatta germanica
probably applies to most species of the Alattide. But this
species differs from Perzplaneta and probably many other forms,
in rotating the capsule, a process now to be described. As
soon as the last egg has passed the vagina and been placed in
the capsule, the latter begins to rotate on its longitudinal axis,
till the crista has described one-fourth of a cylinder to the right.
The capsule is now in a horizontal position having its greater
transverse diameter parallel with the corresponding transverse
diameter of the insect’s body. The abdomen contracts during
oviposition, and its end comes to lie anterior to the tips of the
wings, so that the broad ends of the latter hide and protect the
protruding end of the capsule. The rotation requires about a
day. In one case a female kept the capsule in a vertical position
for two weeks, apparently from some inability to revolve it. In

402 WHEELER. (Vor. If.

all other cases the capsule was regularly turned to the right,
never to the left.

The female Periplaneta orientalis drops the capsule soon after
its completion, with predilection in some food supply, such as
flour or meal. Slatta germanica carries it for about a month,
then drops it shortly before the hatching of the larve. Some
writers claim that the parent assists the young in escaping from
the capsule, but I have proved by many experiments that the
expanding and struggling of the young insects are amply
sufficient to separate the feebly united lips of the crista. Such
an instinct in the female would be of use only if the lips of the
capsule could not be opened by the young. Taschenberg (46)
claims that the female regularly lays only one capsule and dies
soon after its deposition. My observations on fifty females,
whose wings were clipped as soon as they had formed their first
capsule, have convinced me that they certainly lay two perfect
capsules as a rule, and possibly more, in the course of the
year.

As will be seen from the preceding account, it is a very easy
matter to orient the eggs of the capsule, to tell just what
position any odthecal egg held in the ovary, or just what position
any egg in the ovary will hold in the capsule. The germarium
pole of the ovarian egg lies just beneath the crista after oviposi-
tion. The concave side of the curved sausage-shaped ovarian
egg is turned to the wall of the capsule, and its convex face, on
which the embryo will appear with its head towards the crista, is
turned to the interior of the capsule and faces the corresponding
surface of the opposite egg. The micropyles which pointed
away from the germarium are on the convex face of the ova-
rian, and on the inner face of the odthecal egg, and point down-
wards away from the crista.

THE DEVELOPMENT OF THE EGG TO THE FORMATION OF THE
BLASTODERM.

Blatta.

The odthecal egg of A/atza, like the ovarian egg, is glistening
white. The latter has been described as sausage-shaped, but
the pressure exerted by the eggs on one another in the capsule
alters their original form very considerably. They assume the

No. 2. } BLATTA AND DORYPHORA. 303

shape of half an elliptical disc, the short axis of which is to the
long axis as 2 is to 3, with a thickness one-sixth of the short
axis (Figs. 36 and 37). The egg is about 3 mm. long, I mm.
broad and 4 mm. thick. Its volume is therefore almost a cubic
millimeter. The cephalic end (Fig. 36 c), recognized by its
evenly rounded contour, is immediately beneath the crista of
the capsule. The opposite or caudal end (Fig. 36 s) is dis-
tinguished by a slight sinus. The ventral face is traversed
by a keel which runs from the cephalic to the caudal extremity
and is most pronounced a short distance below the middle of
the egg. The dorsal surface is flat and evenly curved antero-
posteriorly. Cross-sections of the ovum are consequently pen-
tagonal (Fig. 40). Thus the eggs can be easily oriented, and
they have a great advantage over spherical or even oval ones,
in that all the earliest developmental changes can be traced
directly to their relationship with the parts of the future
embryo. This is of the highest importance in the early stages.

It will have been observed that a complete reflexion of the
egg takes place during oviposition as the concave face of the
curved ovarian egg becomes the convex back of the odthecal
egg, and the convex micropylar face of the former becomes the
straight, carinated, ventral face of the latter.

Yolk. —I have not been able to observe a passage of fol-
licular epithelial cells into the egg to form yolk by their dis-
integration, as has been described by Will (51) in WVepfa and
Notonecta, and by Ayers (1) in Gcanthus. There is only one
layer of cells in the follicular epithelium of S/atta, and as this
persists till after the chorion is completed, no migration of nu-
clei into the yolk, or even disintegration of nuclei at the surface
of the egg, is observable. All of the yolk in S/atta (excepting
those portions derived from the germinal vesicle ?) is secreted by
the protoplasm of the epithelial cells, not as yolk, but as sub-
stances which are taken up by the growing ovule, and again
secreted in the form of the bodies to be described presently.
During this process of yolk-secretion, the epithelial cells re-
main intact, their slow disintegration not taking place till after
oviposition, when their compacted and yellowish remains have
assumed the appearance so suggestive of the corpora /utea of the
Mammalia. :

The yolk of the eggs of B/atta has been studied by Patten

304 WHEELER. [Vok. III.

(38) and Blochmann (5). The former has described the physical
structure; the latter, the peculiar bilateral distribution of the
yolk elements. Though my researches have revealed only
a few new facts concerning the yolk, I will give them in their
entirety.

In the young ovarian egg, 0.5 mm. long, the nucleus is
surrounded by granular protoplasm in which no yolk has
developed. In eggs 1 to 2 mm. long the yolk consists of two
kinds of bodies: transparent fat globules of various sizes, and
a translucent albuminous substance broken up into distinctly
outlined masses which are polygonal in form from mutual
pressure. Beneath the follicular epithelium is a layer of small
albuminous masses enveloping the interior yolk. This is ata
time when the large nucleus is disintegrating. By the time the
egg has reached its full size, the yolk has assumed the highly
differentiated structure best studied in the oodthecal egg.

The yolk of a fresh mature egg crushed between the slide and
the cover glass in its own liquids, or in normal salt solution, shows
an abundance of different sized highly refractive oil globules,
and a greater number of distinctly outlined albumen spheres,
which are polygonal in the intact egg where mutual pressure
prevents them from taking on the spherical shape which they
seem to be continually striving to assume. These albumen
spheres are thin-walled sacs full of a thin liquid in which float
multitudes of small, irregular granules. Sometimes small oil glob-
ules are enclosed. That the contents of these sacs is a thin liquid
is proved by the exceedingly active Brownian movement of the
irregular granules, a movement which is certainly constant in
almost all these vitelline bodies in the living egg. But these
bodies are far from being alike in structure. In some few the
granules are very minute, closely packed, and exhibit no
Brownian movement; in others the granules are large and dis-
tinctly irregular, few in number, and possessed of a tendency to
unite in flakes which hang suspended in the thin liquid filling
the sacs. In the great majority of these bodies, however, the ©
mean between these two extremes in structure is maintained. It
is probable that the granular forms arise from the dense homo-
geneous bodies by chemical decomposition. This decomposi-
tion, which is accomplished, as I said above, in the ripe ovarian

egg, takes place in different parts of the egg in different degrees,

No. 2.] BLATTA AND DORYPHORA. 305

thus bringing about the peculiar bilateral structure first noticed
by Patten and subsequently described- by Blochmann. In
hardened eggs the granules have the appearance of nets with
larger or smaller meshes (Figs. 23, 24, etc.). This structure
is best seen in cross-sections of eggs hardened in alcohol or
picrosulphuric. acid.

For the distribution of the above-described yolk-elements in
the egg I cannot do better than quote Blochmann’s succinct and
accurate account. He says: ‘Die Hauptmasse des Dotters
ercheint auf dem Querschnitt [see my Fig. 40] etwa als gleich-
schenkeliges Dreieck, das seine unpaare (kurze) Seite nach
aussen, seine Spitze der Mitte zukehrt. Diese Dottermasse
besteht aus durch gegenseitigen Druck polygonal abgeplatteten
Korpern, deren Umrisse besonders an den peripheren Par-
tien deutlich sind, wahrend sie in der Mitte des Eies mehr
oder weniger zusammenfliessen. In den peripheren Regionen
zeigen diese Korper eine feine Granulirung ihrer Sub-
stanz, wahrend sie im Innern des Eies vollstandig homogen
erscheinen. Sie farben sich bei der gewohnlichen Behand-
lung mit Boraxkarmin ziemlich intensiv. Umgeben wird diese
Dottermasse von einer Zone [my Figs. 39 and 4o] von eben-
falls polygonalen Elementen, die jedoch iiberall deutlich unter
sich und von den Elementen (der Hauptmasse des Dotters)
sich abgrenzen. Sie zeigen eine grobnetzige Struktur und far-
ben sich mit Boraxkarmin nur ganz wenig. Diese Zone des
Dotters hat ihre grosste Dicke tiber der Spitze des von dem
anderen gebildeten Dreiecks und nimmt nach den Seiten zu ab,
um in der Mitte der Riickseite wieder etwas an Miachtigkeit
zu gewinnen. Dieser blasse Dotter bildet also einen kontinu-
irlichen Mantel um den anderen. (Es) finden sich langs
der ganzen Eioberflache zwischen die blassen Dotterkorper
eingelagert einzelne starker farbbare Elemente des Dotters
(der Hauptmasse) oder auch kleine Gruppen von _ solchen.

Unregelmassig durch beide Dotterarten finden sich
zahlreiche grossere und kleinere Fetttropfen, die an den
Praparaten als Hohlraume erscheinen, da das Fett durch die
Behandlung mit Chloroform, Terpentinol, etc. aufgelost wird”
(nly Pigs: 23;°24,,etc.):

The ventral thickening of the “continuous mantel” of granular
yolk polyhedra, which surrounds the wedge-shaped central mass

306 WHEELER. [Vo. III.

of translucent polyhedra, is a pre-arrangement for the reception
of the blastoderm, and more particularly the future embryo.
The vital activities, which, in forming the embryo, finally be-
come centred on the ventral face of the egg, find the yolk here —
already sufficiently decomposed to admit of easy metabolism into
protoplasm. Later, in eggs with advanced embryos on their
ventral faces, the granular yolk has again become transparent
and homogeneous in extensive masses which arise from the con-
fluence of many of the polyhedral bodies. I differ from Bloch-
mann in maintaining that the granular yolk is originally derived
from the homogeneous variety. He was led to infer the oppo-
site process from his study of the yolk in ants’ eggs.

Protoplasm.—In young ovarian eggs, 0.25 to 0.5 mm long,
the cytoplasm is finely granular. The deutoplasm begins to
accumulate, and by the time the egg has become 1 mm long,
the above-described vitelline bodies and oil globules have de-
veloped in such numbers as to reduce the protoplasm to an
exceedingly delicate net. In the mature egg the Kezmhaut
described for so many insects’ eggs is a layer so thin that it is
just perceptible on the centre of the dorsal surface and at
the cephalic pole (Fig. 4 gv). This protoplasmic layer is full of
what I shall call Blochmann’s corpuscles. They are minute rod-
shaped bodies so numerous in the surface protoplasm as to make
it appear reticulate. They Jook like bacillar micro-organisms,
stain deeply, and according to Blochmann, who is probably right
in thinking that they play an important role in the development
of the egg, multiply by transverse division (like Bacteria).
Weismann was the first to note these bodies in Diptera in 1863.’
Blochmann (3, 4,) called attention to them in 1884 and 1886, in
the eggs of Camponotus and Formica, and in 1887 in Llatta, Peri-
planeta, Pieris, Musca, and Vespa. In the three last genera the
bodies are spherical. In several of Stuhlmann’s (45) figures,
these bodies are prominent. In &/atta I have found them wher-
ever the peripheral layer of protoplasm is perceptibly thickened,
especially surrounding the polar globules on the middle of the
dorsal surface (Figs. 14, 15, and 16), and at the cephalic end of the
egg (Fig 4 77). They seem to be made of more rigid material
than the protoplasm in which they are embedded, for they pro-
trude as very minute prickles from the surfaces of eggs hardened
in Perenyi’s fluid. I have not been able to trace out their der-
ivation and ultimate destiny.

No. 2.] BLATTA AND DORYPHORA. 367

As the granular yolk polyhedra of the ventral portion of the
egg are much smaller than the homogeneous ones of the in-
terior, there is more protoplasm in the ventral part of the egg.
The internal portions crumble very easily in sectioning, and
I am hence inclined to think that very little or no protoplasm
extends in between these bodies from the periphery. Thus we
see that the distribution of the protoplasm, as well as the yolk,
is in accordance with the position of the future embyro. Later,
when cells appear in the egg, their amceboid cytoplasm con-
sists of evenly granular protoplasm, faintly stainable in borax
carmine.

Karyography of the Egg.—In studying the changes in the
nucleus, it has proved to be impossible to preserve the finest
cytological details, since the ovarian eggs of lata, like the
eggs of the Orthoptera in general, are not easily sectioned un-
less hardened in Perenyi’s fluid, as the yolk is exceedingly
friable. Perenyi’s and Kleinenberg’s fluids do not preserve the
karyokinetic figures perfectly, but cause the loops of chromatin
to fuse in masses. On the other hand, the achromatic spindles
are often beautifully distinct. Any discrepancy between Bloch-
mann’s figures of the polar globules and mine, is probably to
be attributed to a difference in the use of reagents.

In young and transparent ova taken from the middle of the
ovariole, the nucleus is seen to’have reached the acme of its
development in volume. It is a large spherical body, more
highly refractive than the surrounding cytoplasm. Its fluid
contents, the karyoplasm, is distinctly separable into two sub-
stances, a liquid karyochylema and an achromatic (plastin ?)
reticulum. In the meshes of the latter is suspended a third
substance, the deeply stainable chromatin, in one large and sev-
eral smaller masses, or in several small irregular particles de-
rived from the former by disintegration. The nuclear wall is
very distinct. Whether it is a membrane or merely a peripheral
inspissation of the karyoplasm is uncertain. When ovarioles
are treated with Fol’s picrochromic acid or Merkel’s chromplat-
inum solution, the whole nucleus contracts and leaves a menis-
coid cavity between itself and the cytoplasm, though it still
preserves its distinct and evenly spherical contour.

In all the following stages the egg, having become opaque,
must be studied in sections, and the history of the nucleus con-

308 WHEELER. [Vion; Tif.

structed from a series of isolated observations. While the yolk
is accumulating, the nucleus becomes amceboid, leaves its posi-
tion at the centre of the egg, and travels to the surface. The
egg is at this time very slightly curved, and the nucleus always
passes to the centre of the concave side. This ameeboid
nucleus is seen in Fig. 6 just after reaching the surface. It is
still large, and does not stain more deeply than the surrounding
yolk bodies. Its long axis:is parallel to the long axis of the
egg. The chromatin, in large masses in the younger egg, has
been reduced to numerous granules of varying size, still recog-
nizable as chromatin because staining deeply in borax carmine.
The pseudopodia are now drawn in, and the nucleus becomes
spheroidal. Soon the face in contact with the surface becomes
cup-shaped, and round masses of a homogeneous substance indis-
tinguishable from the surrounding yolk bodies fill the cavity
(Figs. 7 and 8 4). In this stage the nucleus is probably giving
off the “maturation spheres” (Reifungsballen), which Stuhlmann
saw given off from the nucleus of so many insects’ eggs (notably
Lepidoptera) ; Will (51) also describes this process in Hemiptera.
In many insects Stuhlmann found that these spheres differed
from the surrounding yolk bodies in power of refraction, etc.
The concavity (Einbuchtung) of the nucleus in A/atta often
contains several of these spheres. Figure 8 represents such a
nucleus seen from the surface, the plane of section being at
right angles to the plane of section in Figs. 6 and 7. Here the
concavity is composed of separate cavities which have fused.
The maturation spheres, after their escape from the nucleus,
mingle with the yolk bodies. Above the orifice in Fig. 8,
at pu, is a small body, denser and more refractive than the
surrounding plasma. I think it corresponds to Stuhlmann’s
paranucleolus. In its centre is a deep red body, probably a
granule of chromatin. In Fig. 9 is seen a nucleus containing two
paranucleoli, pz, destitute of the central granule. I cannot say
what becomes of these bodies. They do not appear in all nuclei
(confer Fig. 7), and are probably evanescent structures formed
and again disintegrated during the mysterious process of nuclear
degeneration. In Fig. 9 granules of chromatin, most numerous
near the point x, are scattered through the karyoplasm. The
disintegration of the nucleus by giving off the maturation

spheres progresses till, when the egg is about 2 mm. long, it is

No. 2.] BLATTA AND DORYPHORA. 309

reduced to a small, somewhat crescentic body, which, unless its
position has been marked, is easily mistaken for a yolk body,
as it in no way differs from the surrounding yolk in ability to
take up coloring-matters. Hence it happens that many investi-
gators have supposed the insect egg to become enucleate at this
time. The resemblance between a yolk polyhedron and the
remains of the germinal vesicle is greatly increased by the gran-
ular contents of both. In the germinal vesicle these granules
are the comminuted remains of the large masses of chromatin so
conspicuous in the young egg; in the yolk bodies they are albu-
minous substances destined, like the other yolk materials, to
become food for the protoplasm. At the very spot where the
nucleus degenerated, viz. at the middle of the concave side of
the egg, there appears in eggs almost mature (2.5-2.8 mm. long),
a cluster of numerous chromatin granules, which I believe to be
the same as those in the germinal vesicle, grown more conspic-
uous by aggregation. Stuhlmann has figured several bodies
like my Fig. 10, representing this aggregation which has pro-
gressed considerably in the centre. These chromatin granules
are probably uniting to form filaments preparatory to karyo-
kinesis. The aggregation takes place in such a way that in
eggs treated with Perenyi’s fluid a narrowly oblong mass of
chromatin is formed, an appearance undoubtedly due to the
fusion of the separate filamentous loops. The oblong mass is
represented in Fig. 11. When the outlying granules have been
added to it, and the achromatic fibrillze have made their appear-
ance, the first polar spindle in the metakinetic stage is completed
(Fig. 12). The axis of the spindle is directed at right angles to
the surface of the egg, which is now mature though still enveloped
in the follicular epithelium. In Fig. 13 the equatorial plate
has divided transversely, whether by longitudinal fissure of the
individual loops or not, I am unable to say, and the two masses
of chromatin are on their way to the poles of the spindle.
Arrived at the poles the masses become spherical, and the
achromatic spindle fades away, while the outer sphere of chro-
matin surrounded by a mass of protoplasm full of Blochmann’s
corpuscles is almost constricted off from the egg to form the first
polar globule. While this is taking place the egg is being freed
from all its epithelium, except the cap at the cephalic pole, im-
pregnated and placed in the capsule. The daughter nucleus of the

310 WHEELER. (Vo. IIf.

first polar spindle remaining within the egg now forms another
spindle directed like: the first. This is seen in\Pie, 14. The
blade of the microtome has somewhat raised the loosely at-
tached first polar globule, the protoplasm of which is seen to
contain many of Blochmann’s corpuscles. The karyokinesis
of the second spindle progresses in the same manner as the
first and the second polar globule is given off, also surrounded
by bacillar protoplasm. The portion of the nucleus which
becomes the female pronucleus, is not seen in Fig. 15, where
only the two polar globules are represented, as it appears in the
next section. Figure 16 is froma surface view of the polar glob-
ules. By comparison with Fig. 14 fg/ 1 it will be seen that they
are lenticular. Here the female pronucleus appears as a more
indistinct body (because out of focus) lying between the polar
globules. The polar globules which I have been able to find in
many eggs taken from the capsules while they were still vertical
in the genital armature (about 6 to 12 hours after the begin-
ning of oviposition) lie in the middle of the convex dorsal wall
of the odthecal egg. They do not divide subsequently to form
what Weismann (48) calls secondary polar globules, but soon
disintegrate. In eggs about one day old their remains may be
found as an amorphous granular mass, lying just beneath the
chorion and entirely separated from the egg.

The female pronucleus increases considerably in size before
leaving the surface of the egg (Fig. 17 9 pz). This increase is
gradual but constant as it makes its way through the dense
yolk of the interior of the egg to the apex of the isosceles tri-
angle of homogeneous yolk abutting on the back part of the
granular ventral yolk. It is on this journey that the female
pronucleus meets the male pronucleus formed from a spermato-
zoon which has entered the egg by one of the funnel-shaped
micropyles on the upper ventral face.

Though I have succeeded in throwing a little more light on
the copulation of the pronuclei than Blochmann, I cannot regard
my observations as completely satisfactory. The process must
be studied in Arthropod eggs with more evenly compact yolk
than the eggs of Orthoptera, the numerous cracks and fissures
in which render the observation of delicate internal processes
exceedingly difficult if not impossible. Moreover, the copula-
tion of the pronuclei in 2/a¢fa is hurried through very rapidly.

No. 2.] BLATTA AND DORYPHORA. 311

In more than a hundred eggs which I sectioned from capsules 6
to 24 hours old I found the greater number in the polar globule
stage and all the remainder, with two exceptions, in the stages
just before, during and after the division of the cleavage nu-
cleus. In the two exceptions which I describe and figure I
found what I take to be the pronuclei. The arrows in the
figures point in the direction of the long axis of the egg, only
the circumnuclear portions of which are represented.

In Fig. 19 the female pronucleus is about one-third the dis-
tance from the cephalic end instead of being in the middle of
the egg where the polar globules are formed. It is no further
from the dorsal surface than the female pronucleus in Fig. 17,
but is much larger. Hence I believe it has travelled up along
the dorsal surface to meet the male pronucleus (Fig. 19 ¢ pz),
which has advanced through almost the whole dorsoventral
diameter of the egg. The female pronucleus exhibits the usual
coiled chromatin filament. The male pronucleus is granular, of
somewhat irregular outline, and surrounded by vacuolated pro-
toplasm. It is rather deeply stainable in borax carmine. In
this Fig. 19 the pronuclei are of very different size, and not-
withstanding the male pronucleus has passed through three-
fourths of the dorsoventral diameter, a distance of ? mm., it has
not increased much in volume when compared with the mass of
the long though attenuated head of the spermatozoon from
which it originated. No astral radiation could be seen surround-
ing these pronuclei. In Fig. 20 we have what I take to be the
two pronuclei conjugating The smaller presumably male portion
of the compound or cleavage nucleus is larger than the male pro-
nucleus in Fig. 19. The place of union is about the middle of
the homogeneous yolk, z.e/ about one-third of the dorsoventral
diameter from the back of the egg. The nuclei of Fig. I9
would probably have fused at a point near the dorsal surface
one-third the distance from the cephalic to the caudal pole, but
the paths of these two nuclei were undoubtedly aberrant. My
observations on single female pronuclei and cleavage nuclei
found at various points along the median dorsoventral diameter
lead me to conclude that the middle of the homogeneous yolk is
the normal point of conjugation. I have represented (Fig. 18)
another female pronucleus from near the point of fusion because
its structure is different from that of the other female pronuclei

R12 WHEELER. [Vot. III.

figured. Its chromatin is limited to a few filaments; whereas
in Fig. 19 2 pz we have a long and intricately wound coil.

The cleavage nucleus continues the course begun by the
female pronucleus. Figure 21 represents it when it has reached
the middle of the dorsoventral axis. The cytoplasm surround-
ing this nucleus, which is drawn from an egg hardened in
picrosulphuric acid, shows an astral radiation. The cytoplasm
passes by insensible degrees into the surrounding homogeneous
yolk substance. It is as if the female pronucleus when it left
the polar globules took a little mass of the protoplasm abun-
dant at that part of the egg’s surface and travelled with it,
making it convert the yolk into protoplasm during the journey.

As soon as the cleavage nucleus reaches the front edge of
the mass of homogeneous yolk, or has advanced a very short
distance further into the granular yolk, it stops and begins
to increase in size till it becomes a clear vesicle (Fig. 22) in
which the chromatin, broken into irregular fragments, lies scat-
tered through the finely granular contents. The nuclear wall
grows fainter and disappears. The large spindle now appears,
and the typical process of karyokinesis is carried on (Fig.
23). The polar axis of the spindle was in all but one of the
many cases in which I observed the division, parallel to the long
axis of the egg. In the exceptional case (possibly an abnormal
egg) it was parallel to the dorsoventral diameter. Even before
the division of the nucleus commences, the polar axis of the
future spindle is foreshadowed, as it were, in the shape of the
granular (amceboid) cytoplasm, which, as may be seen in Fig.
23 cf, is elongated in a direction parallel to the cephalocaudal
axis of the egg. The karyokinetic process employed in this
and the subsequent divisions is typical. Soon after the nuclear
wall again makes it appearance the two nuclei with the cytoplasm
which surrounds them separate about one-fifth the longitudinal
diameter of the egg, and then prepare for the next division.
The polar axes of the two daughter spindles now formed are very
nearly at right angles to the polar axis of the mother nucleus.

In all the first divisions the perfect isochronism of the differ-
ent stages in the different nuclei is striking. Fig. 24 represents
two spindles from an egg containing four nuclei in exactly the
same (metakinetic) stage. In this figure, taken from a longitu-
dinal section, one of the spindles (c) has its axis at right angles

No. 2.] BLATTA AND DORYPHORA. 313

to the longitudinal and also to the dorsoventral axis of the egg.
The loops forming the equatorial plate are readily seen and
counted. Ten in number, each probably attached to an
achromatic fibril, they are arranged in such a manner that
seven form a circle inclosing the remaining three.

The divisions of these four products of the cleavage nucleus
continue till about 60 to 80 cells have been formed, scattered
irregularly through the granular ventral yolk. The axes of
the spindles are inclined in various directions, and nothing in-
dicates an early differentiation into cells destined on the one
hand to remain in the yolk, and on the other to form the
blastoderm.

The numerous amceboid cells next migrate to the surface of the
egg. In Fig. 25, representing the ventral third of a median cross-
section, two of these cells have just reached the surface, while
one is still on its way. On reaching the surface the cells first
become sqmewhat conical, and then gradually flatten out. The
tension of the cytoplasm is so great that the inclosed nucleus is
forced to become lenticular (Fig. 26 a). The cells which have
reached the surface, and are much scattered over the roof-shaped
ventral face and the adjacent portions of the lateral faces, com-
mence dividing tangentially, not by karyokinesis, as heretofore,
but by akinesis. Figure 36 represents the lateral surface view,
and Fig. 26 part of a transverse section of an egg in this stage.
The division of the nuclei which have reached the surface is
very rapid, and compact colonies of cells of different sizes and
in different stages of the unequally constricting process charac-
teristic of akinesis may be seen embedded in amceboid masses
of protoplasm. I have given such a syncytium (enlarged from
Fig. 36) in Fig. 34, and two of the dividing nuclei from other
parts of the same egg in Fig. 35 4,c. The method of division
is exactly like what was described above for the cells of the fol-
licular epithelium (Fig. 5), omitting the peculiar nucleoli which
I have not been able to detect in these nuclei. My observa-
tions tend to show that all the future divisions in the formation
of the blastoderm and those subsequently undergone by the
serosa are akinetic, the densely coiled chromatin filament re-
maining inert, and the division taking place by a constriction
which often produces two daughter nuclei of very unequal size.
I emphasize the fact that these forms of division could not have

314 WHEELER. [ VoL. IE.

been produced by reagents, as these eggs were hardened in
picrosulphuric acid or simple alcohol, which in younger and
older eggs preserve the karyokinetic figures of the cleavage
nucleus and its immediate descendants with great clearness.

The nuclei of the small syncytia spread apart evenly over the
surface of the egg, which now presents the appearance of Fig.
37. The pseudopodia of the amceboid cytoplasmic masses run
together to form a net. The egg is now in the blastema stage
of Patten (38). The cells at the surface are being continually
reinforced by cells migrating from the yolk. Ever since the
first division of the cleavage nucleus the nuclei have undergone
a gradual and steady diminution in size, and this progresses till
the formation of the blastoderm which takes place by the
division of the blastema cells. In this stage the yolk is covered
with a layer of protoplasm, imperfectly divided into small cells,
each containing a lenticular nucleus, which in turn contains two
very deeply stainable nucleoli (Fig. 33). Fig. 27 is a trans-
verse section through the front of an egg in the blastoderm
stage. All the protoplasm at the surface of the egg is carried
there by the migrating cells or formed from the surface yolk
through their influence, as the Kezmhaut, so highly developed
in Doryphora, as will be seen further on, is undeveloped on the
ventral, lateral, and all but a very small portion of the dorsal
surface of the egg of Blatta germantca.

All the nuclet, formerly in the yolk, probably rise to the sur-
face to form the blastema and reinforce it in its formation of
the blastoderm. Before the blastoderm is completed, cells sep-
arate from it and pass inwards to form the yolk cells, or
vitellophags. The following are my reasons for believing that
all the products of the cleavage nucleus go to the surface. The
cleavage nucleus cells have large pale nuclei and distinctly
amoebiform cytoplasm, like those in the yolk of Figs. 25 and 26.
Subsequently none of these nuclei are to be found in the yolk,
but in their stead occur at greater or lesser distances from the
ventral and lateral faces small deeply stainable nuclei of exactly
the same size as the blastoderm nuclei, not surrounded with
amoebiform cytoplasm, but apparently melting their way through
the yolk, often in the middle of a dense yolk body, and, above all,
exhibiting the same intimate structure as the blastoderm nuclei
(Fig. 28). When treated with picrosulphuric acid, these centrip-

No. 2.] BLATTA AND DORYPHORA. 315

etal nuclei show the two highly refractive nucleoli of the
surface cells; when treated with alcohol only, both the surface
and yolk nuclei exhibit the same closely wound, deeply stainable
chromatin filament. Such exact similarity in size, shape, and
minute structure is very strong evidence in favor of community
of origin. Still I have not been able to find an egg without
nuclei in the yolk, notwithstanding I sectioned many eggs in
the blastoderm stage. I am inclined to think that such a stage
may not occur, but that the last of the cleavage nucleus
products go to the surface simultaneously with the passage in
the opposite direction of the first blastoderm products. Thus
the enucleate yolk stage would be slurred over.

The time required for the development so far described is
approximately as follows: The first polar spindle is formed in the
ovaries ; the second polar spindle during oviposition. Both polar
globules have been constricted off by about the sixth hour from
the commencement of oviposition. By the end of the first day
the female pronucleus has fused with the male pronucleus, and
the cleavage nucleus thus formed has reached the back of the
granular ventral yolk. The products of the cleavage nucleus
are formed and reach the surface by the end of the third
day. By the end of the fourth day the blastema is completed.
During the fifth day the blastema nuclei proliferate and
complete the blastoderm by the close of the sixth day. The
development is, of course, accelerated by a rise and retarded by
a fall in temperature, though not to the extent observed in
many other animals.

Before passing over to a description of the early stages of
the egg of Doryphora, I will recapitulate the movements of the
nuclei by means of diagrams of a longitudinal and equatorial
cross-section of the egg (Figs. 39 and 40). In these diagrams
a is the cephalic, 6 the caudal end, ¢ the ventral, d the dorsal, 0
the lateral surface. The shaded body / is the homogeneous
yolk, the dotted portions y the granular yolk. The germinal
vesicle starting from the central point e goes to the surface,
describing the path represented by the line ef Here it gives
off by two successive divisions the two polar globules /!
and f%, and then as the female pronucleus turns back to
go in the opposite direction. The line representing the pas-
sage of the germinal vesicle to the surface is really too long,

316 WHEELER. (Vor. IIL.

as this path is travelled over when the egg is much smaller,
and the distance from the centre to the periphery much
less than in the mature egg. The nucleus of the sperma-
tozoon entering the egg at some point on the ventral surface
between s and c, probably at or near #, advances through
the egg as the male pronucleus z and fuses with the female
pronucleus, coming from the opposite direction, at a point
near & The segmentation nucleus passes on -to the point
/ and divides in the direction of the anteroposterior axis of
the egg, giving rise to the daughter nuclei wm. By sub-
sequent divisions these give rise to the blastema nuclei, which
migrate to the ventral and ventrolateral surfaces of the egg (7).
It is by a tangential division of the blastema cells, forming a
layer of much smaller cells, which creep around the sides of
the egg and close on the dorsal surface, that the blastoderm is
completed.

DoRYPHORA.

Turning now to Doryphora, we find that the ovariole differs
from that of A/attfa in one particular: The terminal thread di-
lates below into a large oval chamber (-udkammer), the mem-
branous wall of which is closely packed with cells of various
sizes, containing nuclei which vary in size as the inclosing
cytoplasm varies in volume. The nuclei contain delicate, much
convoluted chromatin filaments. Besides the difference in size,
no other differences are perceptible between the different
cells.

At the lower end of the Exdkammer the differentiation of
the cells into ova and follicular epithelium takes place. Careful
examination of many sections has convinced me that none of
the peculiar phenomena described by Will (51) in the oogenesis
of Wepa are to be observed in Doryphora. What I have seen
is in perfect accord with Leydig’s observations (29). The large
cells of the Exdkammer become the ova, and the smaller cells,
after undergoing a further reduction in size by division, become
the follicular epithelium.

In the two upper follicles the ova resemble in every respect the
large cells of the terminal chamber, the nuclei retaining exactly
the same perfectly spherical form, and the same distribution of
their chromatin. In the ovum of the third follicle the chromatin

No. 2.] BLATTA AND DORYPHORA. 317

has assumed a different appearance. It is no longer distributed in
the long, even, much convoluted filament, but has broken up into
several spherules which stain more deeply. One or more large
vacuoles are to be found in each one of these nucleoli, or masses
of chromatin, which under a high power seem to hang suspended
in the meshes of the nuclear reticulum in the same manner as
the homologous bodies of Alatta. From the time of its first
formation till the ovum has attained a considerable size, the fol-
licular epithelium is columnar with its elongate nuclei directed at
right angles to the long axis of the egg. Later the epithelium
flattens, and the nuclei become kidney-shaped, with their long
axes tangentially directed to the surface of the egg and their
hili directed inwards.

The yolk first makes its appearance in the form of numerous
granules. In no case have I seen a degeneration of the follic-
ular epithelium to form yolk. The large granular yolk spheres
soon make their appearance. As these bodies are much smaller
than, but in other respects very similar to, those in A/a/ta, I
have given little attention to their study. Though the proto-
plasm is reduced to a very delicate reticulum by the great ac-
cumulation of yolk spheres, there remains till the formation of
the blastoderm, contrary to what I have observed in 4/atta, a
thick layer of finely and evenly granular protoplasm, which en-
velops the whole egg and is equivalent to Weismann’s Kezmhaut,
though it is present from the first appearance of the yolk in the
form of spheres, and does not originate just before the forma-
tion of the blastoderm, as in several of the insects studied by
Weismann (47). The thick surface layer stains pale pink in
borax carmine, and is quite distinctly marked off from the retic-
ulate yolk-charged protoplasm of the interior of the egg.

After the nuclear filament has become metamorphosed into
the spherical vacuolated masses above described, the nucleus
moves from the centre of the egg to the surface, travelling along
a line at right angles to the polar diameter of the egg. It thus
reaches a point midway between the poles, taking the same
position as the germinal vesicle of A/atta. During its migra-
tion the karyoplasm becomes amoeboid, and except at its outer
surface retains its irregular form even after taking its position
right under the follicular epithelium. The outward directed
face becomes excavated, the rest of its surface remaining con-

318 WHEELER. (Vou. IL.

nected with intervitelline protoplasmic trabecule (Fig. 56 77).
The karyoplasm of the nucleus is coarsely granular. In the
nucleus figured only two of the vacuolated masses of chromatin
(or nucleoli, as most writers call them) are present. The larger
contains six vacuoles, one of which incloses a bar-shaped mass
of chromatin (Fig. 56 7/7). Inthe cavity of the nucleus a number
of more or less oval hyaline masses are seen. They are doubt-
less the equivalents of the “ maturation spheres,’ noted above
in Blatta. Stuhlmann (45) has found these same spheres in
the degenerating germinal vesicle of ZLzza, a Chrysomelid allied
to Doryphora.

The next stage found in the decomposition of the germinal
vesicle is represented in Fig. 57. The karyoplasm has become
confluent with the intervitelline protoplasm, and only the chro-
matin portion marks the spot where the nucleus reached the sur-
face of the egg. The larger yolk spheres, formerly present even
in the surface protoplasm, have passed inwards, and only the
smaller spheres still remain in what is to become the blastema.
Soon these, too, retire further into the egg, and the surface pro-
toplasm is marked off from the vitelliferous portion. The re-
mains of the nucleoli are worthy of attention. The vacuoles have
disappeared, and the glistening chromatin has grown denser,
and stains very deeply. In the case figured, one or two nucleoli
have evidently broken into the nine fragments of different sizes
and shapes. The larger and more peripheral mass (Fig. 57 72)
is surrounded bya pale aureole. Its size, position, and the
clear protoplasm surrounding it, seem to point it out as the im-
portant and permanent mass of chromatin soon to be converted
into the first polar spindle. The remaining eight fragments
seem to be leaving the surface and passing into the yolk, where
they probably disappear, as no traces of them can be found in
succeeding stages.

In Fig. 58, which represents the next stage in the nuclear
metamorphosis, we find that the mass # of Fig. 57, which con-
tained five spherical masses of dense chromatin, has become a
perfect oval nucleus in the resting stage. The chromatin has
again passed into the filamentous state. The surface layer
of protoplasm is clearly developed and has secreted the vitelline
membrane (Fig. 58 v). The chorion, too (Fig. 58 ch), has ap-
peared. The follicular epithelium which secreted it is omitted
in this and the next figures.

No; 2:'] BLATTA AND DORYPHORA. 319

The resting nucleus just described soon begins to divide. Its
small size prevents an accurate understanding of the peculiari-
ties of its mode of division. Enough can be gleaned from Fig.
59, however, to show that the karyokinesis is not typical like
that described by Flemming (12, 13) and Rabl (41) for the
epithelial nuclei of Sa/amandra. No loops seem to be present
in the metakinetic stage, but the chromatin is arranged in mo-
niliform strings, each of which seems to be applied full length
to one of the achromatic fibres of the spindle. I have not seen
all the stages in the metakinetic process.

In the next stage observed (Fig. 60) the two masses of chro.
matin resulting from metakinesis have reached the poles of the
spindle, where the fibres before apparent have become invisible.
In the equatorial plane, however, the achromatic filaments are
very distinct, being noticeably thickened. This thickening of
the spindle fibres to form the dividing plate (4) between the two
cells is of universal occurrence in plants, as may be seen from an
examination of Strasburger’s (44) delicate figures. It is, how-
ever, not infrequent in Arthropods. Carnoy (g) figures many
instances in his “ Cytodiérese.”

Unfortunately I have been unable, through lack of material,
to trace the changes of the nucleus immediately following those
just described. The ovum is deposited by the female Doryphora
with its nucleus is the stage represented in Fig. 60 (compare
Blatta). The outer mass of chromatin (/!) must be regarded
as the first polar globule. Probably the process of forming the
second polar globe is essentially the same as in A/atta.

Though incomplete, my observations prove, I think, that polar
globules are also formed in the Coleoptera, thus adding another
order of insects to the three in which these interesting bodies
were found by Blochmann (5).

As in 4/atta, the nuclei represented in Figs. 57 to 60 are very
small and difficult to find in the enormously larger eggs.

Long before oviposition the eggs of Doryphora have acquired
the dull orange color which makes them so conspicuous on the
under surfaces of the leaves to which they are glued by the
females. The coloring-matter is seated in the yolk bodies, and
ultimately disappears in eggs preserved in 70 per cent alcohol.
The eggs are most deeply colored in living specimens in the
earlier stages, and a gradual fading of the color accompanies the

320 WHEELER. EVOL. IL:

gradual metabolism of the deeply colored yolk into pale yellow
protoplasm.

As the yolk spheres are much smaller in Doryphora than in
Llatta, mutual pressure does not make them so clearly polygonal.

Though granular, the protoplasm, which is spread in such a
thick layer over the surface of the yolk, contains none of the
bacillar bodies so easily demonstrated in 4éatfa. It is of course
possible that in the beetle’s eggs they may be present, but of
much smaller size and of spherical shape like those found in the
Lepidopteron Pzervs.

The chorion in Doryphora is thick and somewhat leathery,
though easily torn with the dissecting-needles. It seems to re-
semble in every way that of Lzza as described by Graber (15).
The surface layer of protoplasm secretes a very delicate and
structureless vitelline membrane, which in the younger stages
is closely applied to the surface of the egg. Soon after the
formation of the ventral plate it is loosened and stands off from
the surface. Besides some clear, irregular patches on the sur-
face of the chorion I have seen no structures which could be
interpreted as micropyles.

As there are strong reasons for supposing that the cleavage
nucleus is situated in the very centre of the egg while dividing,
the copulation of the pronuclei must take place along the radial
line joining the centre of the egg to the point where the polar
globules are formed. As I possessed no eggs immediately after
oviposition, the phenomena of pronuclear conjugation, which
could probably be more favorably studied in the eggs of Dory-
phora than in 4latta, on account of the perfect and even sec-
tions obtainable, were not observed.

The first stages after the one given in Fig. 60 which I have
been able to find in my material showed the division imme-
diately following the first and second divisions of the cleavage
nucleus. As the few nuclei were all near the centre of the egg,
and as Graber has found the cleavage nucleus is the centre of
the very similar eggs of the allied Zzza, I feel justified in believ-
ing that this is the point at which the first division occurs. The
products of the cleavage nucleus go through karyokinesis, but
owing to their much smaller size the process is much less dis-
tinct than in A/atta. In eggs stained with borax carmine, the
cytoplasm of each cell appears as a delicate pink cloud among

No. 2.] BLATTA AND DORYVPHORA. 321

the grayish yolk spheres, and very high powers are necessary to
detect the delicate rays of the spindle or even the minute gran-
ules of chromatin in the metakinetic and succeeding stages.

The isochronism among all the nuclei in the different stages
of development up to the formation of the blastoderm is quite
as apparent as in Satta. Judging from the great number of
eggs with resting nuclei and the very few eggs with kinetic
figures, I conclude that division takes place very rapidly and is
followed by comparatively long periods of quiescence.

Fig. 61 represents one-half a cross-section through the equa-
torial region of an egg containing a number of nuclei in its yolk.
All the nuclei are resting and are surrounded by ameeboid
masses of protoplasm. These cells often have the appearance
of being in motion, most frequently in concentric paths. The
nucleus is in the broader portion of the comet-shaped cell,
which seems to be advancing head foremost. These cells are
surrounded by numerous minute vacuoles that under the low
power, with which Fig. 61 was drawn, appear like coarse granules.

These cells divide rapidly and give rise to many smaller cells
scattered through the whole yolk. A few enter the blastema
layer and begin to proliferate rapidly. As soon as this mi-
gration to the surface has taken place, the cells which have
remained in the interior, and whzch do not go to the surface, stop
dividing and take up positions at short but nearly equal distan-
ces apart, through the whole yolk. Before assuming their defi-
nite positions they have multiplied so rapidly that one may
frequently see strings of three or four cells (Fig. 62 yz}).
Often, too, in this stage most of the cells are in pairs, or, more
accurately speaking, the egg contains many binucleate cells.

The nuclei which have entered the surface layer of pro-
toplasm divide tangentially. Sometimes the axis of the spindle
is inclined at an angle less than go° to the radius of the circular
cross-section, but in no case have I seen a spindle with its axis
directed radially. The first divisions of the nuclei, which have
entered the blastema, give rise to an even layer of cubical cells.
By one more division of its constituent elements this blastema
is converted into the blastoderm, which consists of smaller and
more columnar cells. Sections taken in all directions through
the egg show the blastoderm to be of even thickness over the
whole surface (Fig. 63).

322 WHEELER. [Vor. III.

GENERAL REMARKS.
a. Nuclear Continutty.

It will be seen from the above descriptive paragraphs, that I
maintain that a portion of the chromatin of the insect egg
visibly survives in the decomposition of the germinal vesicle and
can be traced through the divisions resulting in the formation
of the two polar globules into the cleavage nucleus and _ its
descendants. This conclusion, which has always been held by
careful investigators of the transparent ova of lower forms, has
been seriously questioned of late by two workers, Stuhlmann
(45) and Henking (20). The former, after investigating a num-
ber of Arthropod eggs in a superficial manner, comes to the
conclusion that a stage exists in the ontogeny of the ovum when
no traces of a nucleus can be demonstrated. Henking not
only indorses this view, but describes in Opz/zo what are cer-
tainly the products of division of the cleavage nucleus as arising
de novo in different parts of the egg.

As Blochmann (5) has pointed out the errors into which both
investigators have fallen with far greater force than I can bring
to bear on the subject, I will not increase the length of my
paper by entering into a detailed account of their observations.
Blochmann’s beautiful researches on the early stages of the egg
have proved beyond a doubt that the Herapoda conform to the
fecundative processes and method of polar-globule formation
observed in other animals.

That there is no moment when the nucleus ceases to extst as
a nucleus seems to me to be proved by my Fig. 11, where the
remains of the nuclear wall are still present while the spindle
is forming. True, the wall is absent in the younger stage, Fig.
10, and Fig. 11 may represent an exceptional case in which the
wall has persisted longer than is usual, but it proves, neverthe-
less, that the matter composing the nucleus does not diffuse
through the protoplasm and ultimately recombine to form the
nuclei which give rise to the blastoderm, as Henking (20) would
have us believe. The nuclear wall is known to persist in
another Arthropod till after the commencement of spindle forma-
tion. I quote the following from the recent work of Weis-
mann and Ischikawa (49): ‘“‘ Auch in den kleinen und dotterlosen

No. 2.] BLATTA AND DORYPHORA. 323

Eiern von Bythostrephes steigt das Keimblaschen bei Eintritt
der Eireife in die Hohe, erblasst allmahlich und zeigt zugleich
an Ejiern, die frisch in den Brutraum iibergetreten sind, den
Beginn der Spindelbildung zzzerhalb des dann noch scharf her-
vortretenden Umrisses des Kleimblaschens.”

The interesting researches of Weismann and Ischikawa (49),
Leichmann’s (28) recent discovery of two polar globules in Ase/-
/us and Pereyaslawzewa’s (40) discovery of polar globules in
Gammarus pecilurus prove that the Crustacea, too, must be
included under the general law.

b. The Law of Orientation.

Though considerable attention has been given to odkinesis in
Echinoderms and Amphibia, no extended observations of these
phenomena in the eggs of Arthropods have , been published.
In view of this fact, r have taken considerable pains to deter-
mine the paths of the pronuclei and cleavage nucleus in 4/a¢za,
and have devoted considerable space to their description.

A perusal of O. Hertwig’s paper entitled, “ Welchen Einfluss
iibt die Schwerkraft auf die Theilung thierischer Zellen?”’ (21),
led me to try experiments to prove whether gravitation has any
appreciable effects in determining the position of the embryo
in the egg, or whether the position of the embryo with refer-
ence to the yolk is predetermined long before, during the de-
velopment of the egg in the follicle.

It has been shown that the eggs of 4/azta are carried in a hori-
zontal position after the first day, so that the ventral or germinal
faces of the upper row of eggs are directed downwards, and
those of the lower row upwards. As the crista is continuous
with the right side of the parent’s body, the heads of the em-
bryos all point to the right’ It occurred to me that by keeping
capsules in various positions any effects of gravitation on the
development of the inclosed eggs could be easily determined.
I accordingly placed capsules in five different positions on a
block of paraffine provided with holes and grooves to keep them
firmly in place. To prevent desiccation, the block was kept in
a camera humida.

Capsules were kept from fourteen to twenty days in the fol-
lowing positions : —

324 WHEELER. [Vot. IIT.

1. Resting with the lateral faces perpendicular and crista
uppermost.

2. Resting on the crista with the tated faces perpendicular.

3. Resting on the left lateral face.

4. Resting perpendicularly on the anterior end.

5. Resting perpendicularly on the posterior end.

In all these cases the eggs developed normally, without the
slightest indication of displacement in position or alteration of
shape in the embryos; whether they were forced to develop
with their heads pointing up or down.

The development was slow in all of the above cases, but this
was not due to the unnatural positions of the capsules, but
rather to the low temperature produced by the evaporation of
the water under the bell-jar. That this was the true cause was
shown by capsules kept under the same bell-jar in the normal
position, on the right side. Their development was likewise
retarded.

We may conclude from these few experiments that the force
of gravitation has no perceptible effect on the development of
the eggs of Aéatta, but that these highly differentiated eggs,
utterly unable to revolve in their envelopes like the eggs of
birds and frogs, have their constituents prearranged, and the
paths of their nuclei predetermined with reference to the parts
of the embryo. As the only difference between the mature
ovarian and the oothecal egg is a difference in shape, we con-
clude that the predetermination is effected before fecundation,
and even before the formation of the first polar globule.

There is nothing in the structure of the newly laid egg of
Doryphora to prove that it possesses a dorso-ventral differentia-
tion like the egg of Avatta; nor are my facts sufficient to war-
rant the assertion that the ventral plate develops on the side
opposite the point at which the polar globules arise. Still the
possibility of such a condition is in nowise precluded, and the
observation of Blochmann and myself on 4/atta probably apply
to the Hexapoda in general. The spherical form of the Crusta-
cean egg as opposed to the oval shape of the great majority of
insect eggs, will be a great obstacle in the way of proving any
similar conditions in this lower group.

It can be proved, however, that we have as true an anteropos-
terior differentiation in the eggs of Doryphora as in Blatta.

No. 2.] BLATTA AND DORYVPHORA. 425,

The eggs are deposited by the females in such a way that the
pole which leaves the vagina first is glued to the surface of the
leaf by a semifluid secretion, which at this point spreads out
into a flat disc on which the egg rests and by which it is
attached. As the hatching larva always leaves the egg head
foremost at the opposite free pole of the egg, and as there is no
revolution of the embryo as in Hemiptera, there can be no
doubt as far as the cephalic and caudal ends are concerned that
the relations of the embryo to the parts of the egg are the
same as those described for B/atta. Moreover, the position of
the eggs on the leaf and the position of the embryo in the egg,
are sufficient evidence that the eggs are oriented in the ovaries
of Doryphora with the cephalic pole directed towards the head
of the mother insect.

Thus I have found that 4/atta completely and Doryphora cer-
tainly in part conforms to the “loi de l’orientation de l’ceuf ”
of Hallez (17), who found that the ova of Hydrophilus and
Locusta lie in the ovaries with their cephalic ends directed
towards the head of the mother insect, and that the dorsal and
ventral surfaces of the egg are predetermined in the ovaries,
Kadyi’s (23) remarks make it certain that Perzplaneta conforms
tothe law. In viviparous Aphzdes the same condition obtains, as
may be gleaned from the plates of Metchnikow (30) and Will
(52). When micropyles are developed at the cephalic pole of
the egg, they form a fixed point which is of great assistance in
observing whether the “law of orientation”’ obtains in a particu-
lar instance. We have sucha case in Corzxva as described by
Metchnikow. In this insect (as also in Affzs), the entoblastic
growth of the embryo somewhat obscures the process; but it
can be readily seen that when the ventral plate forms, the por-
tion of it which will subsequently grow out into the procephalic
lobes is situated at the micropylar pole, which is anteriorly di-
rected while in the body of the mother insect. The growing into
the yolk of the embryo tail first brings the head to the opposite
end of the egg, but during revolution the embryo regains the
position which it held before the formation of the amnion and
serosa (see Metchnikow (30), Plates XXVI. and XXVII.
Pacs.G, 01,20; 25, 27).

326 WHEELER. [Vor. III.

THE FORMATION OF THE GERM LAYERS AND EMBRYONIC
ENVELOPES.

Doryphora.

As my observations on the formation of the germ layers in the
potato-beetle are both more copious and more satisfactory than
in Blatta, and as Doryphora probably represents more nearly
the typical process of germ layer formation, I will begin my
remarks on this subject with Doryphora, and append what I
have to say on Liatta.

The first change visible in the blastoderm from the surface is
the appearance of a pair of folds which arise on the middle of
what is to be the ventral surface of the egg (Fig. 66). The two
folds may best be described as resembling a pair of but slightly
bent parentheses close together. In cross-sections these folds
are scarcely perceptible, and the difference in thickness between
the ventral and dorsal blastoderm is very slight.

Soon the folds became more decided (Figs. 67 and 68), their
anterior ends are continued around and meet so as to inclose
a spade-shaped space, while their posterior ends diverge and are
continued in the opposite direction to the caudal end of the egg,
where the depression inclosed between the two folds turns
inward and ends abruptly. The depression inclosed by the
fold is to become the groove-shaped gastrula. The nuclei of
the blastoderm now present a very different appearance from
that represented in Fig. 66. The fold-surrounded depression
at the anterior end (Fig. 67 a), lying where the stomodeum
is subsequently invaginated, is apparently a differentiated por-
tion of the gastrula, to judge from its peculiar shape. In
lateral view (Fig. 68 a) this portion of the blastoderm is seen
to be concave, the nuclei are closely aggregated, whereas an-
teriorly and posteriorly they are much scattered and have
increased in size. The true distribution of the cells, as shown
by their nuclei, is best seen in the lateral view of the same
egg (Fig. 68). The aggregated mass of cells, or the ventral
plate as it may now be called, is clearly marked off from the
serosa or remaining blastoderm, which is recognized by its
larger and more scattered nuclei. The ventral plate is seen
to be constricted toward the middle of the egg to form two

No. 2.] BLATTA AND DORYPHORA. 327

~

lobes ; the anterior broader and shorter is the procephalic, and
the posterior and longer the abdomino-thoracic lobe. In both
views of the egg (Figs. 67 and 68) a number of lines are seen
crossing the ventral plate at right angles to the longer diam-
eter. These lines make the plate appear segmented, and at
first reminded me of Kowalevsky’s figure (Plate VIII., Fig. 2),
which represents an embryo //ydrophilus in exactly the same
stage as that which I have figured. More careful examination,
however, convinced me that the lines were not due to segmen-
tation, nor, in fact, depressed at all, but were the wrinkles into
which the ventral plate was thrown, probably by a contraction
away from the anterior pole.

The simple method by which the ventral plate is formed is
easily seen in a median cross-section of an egg in the stage fig-
ured in Fig. 67 (Fig. 64). The small projection 7 is the ridge
which separates the thick and sinking gastrular portion of the
blastoderm (g) from the remainder of the layer. As we have
seen, all the cells of the completed blastoderm are columnar. The
thickened ventral plate is formed merely by the cells on the
ventral surface of the egg lengthening in a radial direction, and
those of the dorsum (Fig. 64 7) changing their shape so as to
have their long axes tangentially directed.

With further development the gastrular groove deepens and
the ridges come close together in the median line (Fig. 70).
The oral end of the gastrula (a) is oval, and is no longer marked
off anteriorly by the ridge seen in Fig. 68. On each side of the
oral widening is seen a small fold (am) between which and
the gastrula the ventral plate cells are much thickened. This
fold is the beginning of that portion of the amnion which sub-
sequently envelopes the head, and the thickenings are probably
the first traces of the brain. The egg (Fig. 70) viewed from
the posterior end discloses some interesting facts (Fig. 69).
The ventral plate has become pushed in at this point, and the
thickened lip thus formed grows forward over it. This lip is
the beginning of the caudal fold of the amnion and serosa. The
gastrular invagination is considerably deeper at its posterior
than at its oral end.

The caudal fold of the amnion and serosa grows much more
rapidly than the cephalic folds. The tail end of the ventral
plate advances dorsally till it is one-third the length of the egg

328 WHEELER. [Vou. IIT.

from the anterior pole. It pushes its way through the yolk in
such a manner as not to bring the amnion or serosa in close
apposition, but to inclose a greater or less amount of yolk
between the two membranes. This dorsal growth of the caudal
end shows considerable variation, however. In some eggs the
end of the tail comes to lie at such a distance from the dorsal
surface that it is almost in the centre of the yolk. In other
instances the amnion and serosa become closely apposed and
extrude the yolk from between them soon after the two enve-
lopes have closed over the mouth, and the embryo has attained
its maximum length.

In Fig. 71 I have represented the much curved embryo in this
stage straightened out. The gastrular invagination has not yet
closed, but it is much narrowed and more lengthened on account
of the greater growth in length of the embryo. The oral end
is still wider than the remaining portion. At the anal end (Fig.
71 x) the groove seems to bifurcate. At the point x the procto-
dzeum is subsequently invaginated. Usually in embryos as old
as that represented the anterior half of the gastrula has closed
completely.

In the embryo figured the cephalic, maxillary, thoracic, and
abdominal portions are already marked out. The first begin-
nings of the three pairs of legs are apparent in the undulating
edge of the thoracic portion of the ventral plate (p! 7? f°). »

A median cross-section of the egg in the stage just described
cuts the embryo at right angles to its long diameter in two
places (Fig. 65). At the posterior end the thick amnion (az)
is separated from the serosa by a layer of yolk (y), which will
shortly be pushed out from either side to join the great central
yolk mass. In this half of the section which is near the caudal
end the gastrula is still open, though its cells have ceased to be
columnar, and are dividing rapidly to form the thick lump of
cells so very conspicuous at this point in slightly later stages.
In the anterior portion of the egg the gastrula has closed, and
the ectoderm and mesoderm are clearly separated. The tubular
walls of the gastrula have broken down to form an irregular
mass of polygonal cells which lie in the median line closely
applied to the outwardly convex ectoderm. Though the clos-
ing of the gastrula progresses from before backwards, the
closure of the oral portion is retarded and is marked by a

No. 2.] BLATTA AND DORYPHORA. 329

narrow oval pit which is visible till the mouth begins to in-
vaginate (Fig. 73 a).

While the amnion and serosa are closing over the oral portion
of the embryo the yolk begins to segment. The first traces of
segmentation are visible on the dorsal surface between the end
of the tail and the procephalic lobes. There the surface of the
yolk assumes a scalloped appearance, and radially directed lines
soon mark the divisions between the yolk balls. The segmen-
tation progresses thence in a ventral direction, both from either
side of the dorsum and directly inwards, so that finally the whole
yolk is reduced to rounded masses, each of which contains from
one to three vitellophags. Each yolk segment is properly a cell
with its protoplasm radiating in all directions as a delicate
reticulum which holds in its meshes the unequal-sized yolk
spheres. By the time the amnion and serosa have completely
formed, all the yolk has been converted into distinct subspher-
ical segments, except the portions immediately under the anal
and oral ends of the gastrula. Here the segmentation remains
for a short time indistinct till the entoderm is established at
these points.

In the embryo with completely closed envelopes (Fig. 73,
Pl. V.) the procephalic lobes (fc/) have grown in size, and
when attached to the egg clasp its upper pole. The three pairs
of thoracic limbs are distinctly formed, while of the cephalic
appendages only the 2d maxillz (mx 2) are beginning to appear.
The base of the attenuated ribbon-shaped abdomen shows traces
of commencing segmentation. Posteriorly it suddenly widens
out into a flat, transversely oval body, which I shall call the caudal
plate. The gastrular invagination is closed except at its anal
end (x 73), and the mouth will soon form at the shallow oval
depression a, which marks the anterior end of the groove.

Fig. 82 represents a longitudinal section through an embryo
a very little older than the one just described (Fig. 73).

The serosa (sv) now covers the entire egg, and is separated
from the embryo proper and the amnion (am). Both mem-
branes present the same appearance in section, being nodulated
with nuclei. The anterior end of the embryo lies on the anterior
end of the yolk in such a position that its mouth (s/) is almost
exactly at the pole; the tail ends somewhat anterior to the mid.
dle of the dorsal surface (vy), The ectoderm, which at its cephalic

330 WHEELER. (Vor. Tit:

and caudal ends (oe and #) passes imperceptibly into the much
thinner amnion, is considerably thickened and has its crowded
nuclei in several rows, though but one row of cells is present.
The depressions which mark off the incipient appendages are
deep and narrow. The mesoderm (msd) is spread out under
the whole of the ectoderm and has begun to thicken under
each somite preparatory to segmentation. It is very noticeably
thickened in two places: under the stomodzeal depression (f/!)
and under the caudal plate (f/?), where it forms a large mass of
cells projecting into the as yet unsegmented yolk just beneath it.
These two masses of cells are the independent sources of the ento-
derm, which grows backwards as two strings from the anterior
mass (pl), and forward as two strings from the posterior mass
(p/*). As we shall see further on, these two strings unite near
the middle of the body and then begin to grow at their lateral
edges till the mesenteron thus formed incloses the yolk.

The points from which the chords grow are plainly seen in
the figure (ez¢! and ent?). Under both points of proliferation
there are a number of nuclei which at first sight under a low
power seem to be dividing karyokinetically. The chromatin is
all aggregated in one or two dense masses in the hyaline karyo-
chylema, and thus resembles the similar aggregations seen in
kinetic nuclei. These nuclei, however, are not dividing, but
undergoing decomposition, as we shall see when we come to
examine a more highly magnified section through the caudal
plate.

Before leaving Fig. 82 I would call attention to the three cells
at c which are on the surface of the embryo in the amniotic
cavity. They are very large and clear, and the more anterior
is apparently creeping in the manner of an Amceba along the
surface of the abdominal ectoderm. These cells, the ultimate
fate of which I have been unable to determine, probably escape
from the anal orifice of the gastrula before it closes. I have
‘im several cases seen such cells issuing from or still in connec-
tion with the infolded pocket of ectoderm, which is called meso-
derm as soon as the outer layer has closed over it (Fig. 87 c).
These peculiar cells may be the homologues of the ‘ Polzellen’
long ago observed in certain Diptera.

A much clearer understanding of the method of formation of
the entoderm may be obtained from Figs. 87 and 88, both rep-

No. 2.] BLATTA AND DORYPHORA. 331

resenting cross-sections through the middle of the caudal plate.
In Fig. 87, from a younger embryo, the gastrula has not yet
closed. Its walls are seen to be much thickened, and the kary-
okinetic figures. show that its component cells are still prolifer-
ating. At the lower surface of the bag-shaped mass the cells
are somewhat less compact and form a layer (ez¢) which at some
points is separated from the superjacent cell-mass. This mass
will give rise to the entoderm, and that above it to the meso-
derm, as soon as the orifice x is definitely closed. [Ve thus havea
mass of cells in which all three germ layers blend, and to no part
of which can be assigned the name of a germ layer. Not till the
groove ts closed have we mesoderm, and not till the lower cells of
the mass have become clearly differentiated from those above them
can we speak of entoderm.

The section Fig. 88 is from an embryo in which three germ
layers are definitely formed, shortly after the closing of the gas-
trula. A depression (7) marks the point where the proctodzal
invagination is to occur. The polygonal mesoderm cells are
spread out in a mass (sd), which is separated by a more or less
distinct line (/) from the entoderm beneath (ext). The differ-
ences between the cells of the last layer and the superjacent
mesoderm are difficult to represent. Their nuclei are somewhat
larger and clearer. They gradually merge into the mesoderm
cells, the boundary being exceptionally clear in the section fig-
ured. Heider (19) says of these same entoderm cells in Hydro-
philus that they are more “succulent” than the mesodermic
elements. This adjective conveys the idea more clearly than
paragraphs of description.

The peculiar nuclei which under a low power seemed to be
dividing are now seen to be ina process of dissolution. TZhey
originate in the entodermtic mass and pass into the adjacent yolk,
where they disappear, sections through slightly later stages
showing no traces of them. From what I have seen I believe
these nuclei to pass through the following stages, examples of
all of which may be found in a single embryo. The karyochy-
lema becomes vacuolated, probably with substances absorbed
from without, to judge from the large size of some of these
nuclei (Fig. 88 v), while the chromatin ceases to present the
threadlike coil and becomes compacted into irregular masses be-
tween the vacuoles. Finally, the vacuoles fuse and the masses of

332 WHEELER. PV OL. TIT,

chromatin, formerly numerous, agglomerate to form one or two
large irregular masses which usually apply themselves to the
wall of the clearly vesicular nucleus (Fig. 88 ¢). The wall of
the nucleus then ceases to be evenly spherical, and becomes
irregular apparently because the karyochylema is escaping
through a rent (Fig. 880). In the last stages seen the masses
of chromatin lie between the yolk bodies, all the other portions
of the nucleus having disappeared. They still take the char-
acteristic deep red stain, but finally become comminuted and
disappear in the intervitelline protoplasm.

The dissolution of these nuclei and their migration into the
yolk is brought to a close soon after the entodermic mass begins
to grow forward.

The oral mass of proliferating cells is essentially the same as
the caudal mass just described; but being smaller, I have not
seen fit to represent it in the plates by enlarged figures. Some
of the entoderm nuclei degenerate in exactly the same manner
as those described in the caudal thickening, but the whole mass
of cells being smaller, the number of these evanescent nuclei is
much less.

I am at a loss to assign a meaning to this migration of de-
generating entoderm nuclei into the yolk unless it be supposed
that originally all the nuclei of the egg went to the surface and
that a portion of the entoderm passed into the yolk to form vitel-
lophags while another portion proliferated forward in compact
sheets to form the walls of the mesenteron. Later, when the
ontogeny was abbreviated in the blastoderm stage by cells being
left in the yolk, this migration of entoderm cells became unnec-
essary, as the yolk, which is already segmented, is copiously sup-
plied with vitellophags. The lack of distinct yolk segmentation
just beneath the two proliferating points may lend some proba-
bility to this view. I am aware that my explanation halts, but
it will have to stand, for the want of a better one, till more facts
are forthcoming on these degenerating nuclei in other forms.

In examining the literature the only observation which I can
find similar to the one just recorded is in Hatschek’s paper on
Bombyx chrysorrhea (18). He observed a mass of nuclei, which
in his figures have all the appearance of undergoing degenera-
tion, just anterior to the large mass of entoderm cells attached
to the oral ectoderm. This mass of nuclei, designated by him
as a “gland,” soon disappears in the yolk.

No. 2.] BLATTA AND DORYPHORA. 333

Blatta.

My observations on the formation of the germ layers in Blatta
are less satisfactory than those on the same process in Doryphora,
because the eggs of the former are difficult to section and have
small, indistinct cells in the later stages. I have, however,
given much attention to the subject, sufficient, I believe, to be
able to assert that the method of germ layer formation departs
from the type observed in Hydrophilus and Doryiphora.

As soon as the blastoderm is completed by the rapid prolifer-
ation of the blastema cells, the whole layer of protoplasm
with its embedded nuclei contracts from the lateral faces
towards the front of the egg. The blastoderm thus becomes
exceedingly thin on the lateral and dorsal surfaces of the egg,
and the nuclei of these surfaces become much scattered and
flattened, while the protoplasm is thickened on the whole ven-
tral face, where the nuclei are crowded together and have again
become spherical. A slight further contraction away from the
cephalic and caudal ends towards the centre of the ventral face
shortens this mass of thickened cells into the ventral plate.

While the blastoderm is thickening, nuclei are being given
off centripetally to form the yolk cells. A few of these nuclei
go deep into the yolk, but the great majority remain at or very
near the surface. They are not given off in a continuous sheet,
nor are they produced from the blastoderm by any invagination.
They are simply nuclei which have been sent into the yolk from
different and often widely separated points of the contracting
blastoderm. The few nuclei which descend into the yolk
remain for a long time small and indifferent. Sometimes the
number of these nuclei is very limited so that they occur in
only a few of a great number of complete longitudinal sections
passed through an egg.

The nuclei of the surface yolk undergo considerable differen-
tiation, and are soon easily distinguished from the superjacent
blastoderm. They surround themselves with stellate cytoplasm,
retain their spherical or spheroidal shape, and often present one
or more large nucleoli (Figs. 29 and 32 v)._ Their function for
many days is the conversion of the yolk into soluble compounds
to be absorbed by the rapidly dividing cells of the embryo.
During this process they grow rapidly, and soon become the

334 WHEELER. (Vo. ITI.

largest cells with the largest nuclei in the egg (Fig. 30 v). The
long pseudopodial continuations of the finely and evenly gran-
ular cytoplasm can often be traced for a considerable distance
between the yolk polyhedra. The yolk cells are never seen
in process of division, and as their number in eggs of widely
different stages is approximately constant, I conclude that they
rarely or never divide.

The thickening process which formed the ventral plate still
continues in a spot about one-fourth the length of the egg from
the caudal end, and gives rise to a rounded mass of cells which
are much thicker than the surrounding portion of the ventral
plate though but slightly raised above the general surface (Fig.
41). <A faint depression appears in the centre of the rounded
mass (4f)._ While this thickening is forming, the nuclei of the
ventral plate are also proliferating very rapidly at two points on
the ventrolateral edges about one-fourth the length of the egg
from the cephalic end (Fig. 41 pct). These cells also increase
in depth, but do not rise above the general surface of the egg.
The two patches of thickened cells are the precursors of the
procephalic lobes. The deceptive appearance of a groove is
presented by the keel (cz), which runs the whole length of the
ventral face, but soon disappears as it is absorbed by the young
embryo.

The formation of the mesoderm can be traced in eggs sec-
tioned during or shortly before the stage figured in Fig. 41.
Figure 38 is a longitudinal section through the posterior portion
of the egg (Fig. 41) through the middle of the thickened mass
of cells and the depression 6p. In this egg the mesoderm has
been forming for some time. The ventral-plate cells are col-
umnar at 0g, and their nuclei are elongated in just the opposite
direction to their former longest axis, which is still the longest
axis of the serosa nuclei at sx. The depth of the ventral-plate
cells gradually decreases anteriorly. The stellate yolk cells are
scattered at various distances from one another under the ven-
tral plate. The mesoderm (sd), as is clearly seen from the
section, arises partly from proliferation of the ventral-plate cells
under 4f and passes forward as a single but incomplete layer
of cells. Towards the head this layer splits, and each of the
two bands thus formed continues forwards under one of the
procephalic thickenings. This is seen in Fig. 31 from a sec-

No. 2.] BLATTA AND DORVPHORA. 335

tion through the point pel of the egg represented in Fig. 41. ecd
is the thickened ectoderm, msd the mesoderm, which is absent
in the middle of the ventral face at c.

That the mesoderm grows forward from the rounded caudal
thickening may be proved by sections through a number of
eggs taken from capsules six and one-half to eight days old.
The eggs will be found in various stages more or less close to
that given in Fig. 41. In some a very short row of mesoderm
cells is found just in front of the thickening ; in others the row
will be longer as it has advanced further to the cephalic end.
Only part of the mesoderm is formed at the thickening. As
can be concluded from the even arrangement of the two layers
anterior to dp in Fig. 38, each ectoderm cell has a mesoderm
cell beneath it, showing that the mesoderm is derived from the
ectoderm by centripetal division. The impulse to this division,
however, seems to originate in the incomplete invagination at
bp and to travel towards the head of the embryo.

After the mesoderm is formed, the depression 6f disappears,
and the amnion and serosa begin to develop. They rise as a
crescentic fold from the rounded posterior edge of the area of
proliferation (Fig. 42 as). The cells of the procephalic lobes
become more prominent, and while the caudal fold of the
amnion and serosa is growing in length and continuing up the
edge of the ventral plate, a fold also arises from the outer edge
of each procephalic area and bends inward. This stage in the
development of these membranes is seen in Fig. 43.

The embryo is now slipper-shaped, the toe of the slipper
being the caudal and the heel the cephalic end. The growth of
the membranes continues, the toe of the slipper completing
itself more rapidly than the heel. Soon the two procephalic
folds are connected around the anterior tip of the ventral plate,
which is undergoing a change in outline. Figure 44 shows the
amnion and serosa almost closed. Over the spot where the
stomodzeal invagination will soon appear, there is still a small,
slit-shaped opening in the membranes, but this soon closes;
not, however, till after the appendages, both cephalic and tho-
racic, have begun to appear.

The structure and formation of the amnion and serosa, as well
as their relations to each other, can be made out from the sec-
tions (Figs. 29, 30, and 32). Figure 29 is a transverse section

336 WHEELER. [Vot. III.

through the point ¢ of Fig. 43, a region at which the two folds
have not yet arisen. The ectoderm (ecd) is very thick, espe-
cially in the median ventral line. The mesoderm (msd@) is
incompletely separated from the ectoderm, and is seen only in
the median portion of the section. The yolk cells are large and
distinct. Their chromatin forms large nucleoli. The yolk under
the embryo is becoming much vacuolated.

The section (Fig. 32) passes through a point a little in front of
as in Fig. 43. This embryo was older than the one represented
in Fig. 42; hence the yolk cell (v) is much larger and the meso-
derm more distinctly separated from the ectoderm. The infold-
ing of the ectoderm to form the amnion and serosa is seen on
either side. The amnion (am) is thicker than the serosa (s7).
Its nuclei are small, close together, and spherical, while the
nuclei of the serosa are large, flat, and scattered. Figure 301s a
section through a point near e! (Fig. 43), of a slightly older em-
bryo. The amnion and serosa are completed and in close con-
tact with each other, so that the yolk cannot pass in between
them. The difference between the nuclei of the amnion and
serosa is very pronounced. The mesoderm (sd), which is
several cells deep, and is now distinctly separated from the
ectoderm, has become an independent layer. Its nuclei are
more spherical than the ectoderm nuclei, many of which are
considerably elongated and flattened.

The entoderm is formed very late in Alatta (about the 15th
or 16th day), and in cross-sections of embryos of that age it
may be seen as a thin layer of cells on either side of the ventral
yolk closely applied to the inner face of the splanchnic meso-
derm (Fig. 54 ext). Cholodkovsky (10) claims that these bands
of entoderm are derived from the splanchnic mesoderm by de-
lamination, but an examination of a number of sections has
convinced me that it is next to impossible to come to any defi-
nite conclusion as to the mode of origin of the entoderm in
Blatta. By the time it has begun to form the cells have become
very minute, and different tissues of very different origins have
become closely united, so that the proximity of splanchnic meso-
derm and entoderm is no proof of the derivation of the latter
from the former. I have been able to satisfy myself, however,
that the entoderm appears in two thin layers, one on each side
of the median ventral yolk, and that these two layers converge

No. 2.] BLATTA AND DORYPHORA. 337

anteriorly and posteriorly, and become united to the inner ends
of the stomodzal and proctodzal pockets, in a manner which
differs in no respect from what is observed in Doryphora after
the entoderm has become definitely established. I can there-
fore see no reason for adopting Cholodkovsky’s view as proving
that the entoderm arises in a manner differing from that de-
scribed above for Doryphora. As far as B#latta is concerned
the question of the formation of the inmost germ layer must
still be regarded as an open one.

The embryo is hammer-shaped when the amnion and serosa
have closed. The cephalic lobes extend around on to the lateral
surfaces of the yolk, and each soon becomes divided into two
lobes, a larger anterior and a smaller posterior one (Fig: 44).
The posterior lobe is the commencement of the antenna (q/).
In many embryos one, or, more rarely, both antennary lobes
are temporarily bilobed (Fig. 44). This may be a slight rever-
sion, tending to show that the antennary lobes originally gave
rise to two pairs of appendages which were perhaps homologous
with the two pairs of antennz in the Crustacea. The mandi-
bles and first and second maxillz are just visible as faint out-
growths of the ectoderm, while the more pronounced three pairs
of thoracic legs have produced a widening of the embryo in the
middle of its length (Fig. 44 /).

The time required for the development described in the pre-
ceding paragraphs is about four days. The blastoderm begins
to contract and thicken on the seventh day from the commence-
ment of development, and by the end of this day the area of
proliferation is formed. Early on the eighth day the amnion
and serosa begin to appear. They develop.rapidly, so that the
embryo is in the slipper stage by the close of the eighth day.
The amnion and serosa are almost or quite closed by the end
of the ninth day. During the tenth day the mesoderm is seg-
mented, and the cephalic and thoracic appendages begin to
appear. The embryonal envelopes are completely formed by
the end of the tenth day, and the embryo has assumed the
shape of a hammer or mallet.

338 WHEELER. . [Vov. III.

GENERAL REMARKS.
a. Germ layers.

Our knowledge of the formation of the germ layers in the
Orthoptera is still less satisfactory than in other orders of
insects, as in most of the species studied even the formation
of the mesoderm has not been clearly determined.

Korotneff (25) failed to find the typical groove-shaped gas-
trula in Gryllotalpa, and Ayers (1) had no better success with
CGicanthus. On the other hand, Bruce (7) has observed the
typical process of mesoderm formation in J/anézs, and Graber (15)
in Mantis and Stenobothrus. Thus only representatives of the
Orthopteran families W/anted@ and Acriditde are known to form
their mesoderm in the typical manner.

Nusbaum (33) concludes, on apparently very little evidence,
that the mesoderm of //a¢ta is formed in the same manner
as in Musca, and he gives a figure of a cross-section with an
immense invagination.

Cholodkovsky (10), in his account of the entoderm formation
in Blatta, says that the gastrula which gives rise to the inner
layer is very easily observed.

As, I spent much time on a full series of stages between
the formation of the ventral plate and the appearance of the
appendages, without being able to find a trace of the elongate
gastrula for which I was searching, I conclude that both Nus-
baum and Cholodkovsky may have been deceived by the carina
on the ventral surface, which, in reflected light, looks like a
narrow groove.

The method of germ-layer formation in AZaféa, at first sight
so different from the method observed in Doryphora, may, how-
ever, be traced to the typical process. My studies on Dory-
phora make it probable that the entoderm of 4/atta originates
in the mass of cells found under the area of proliferation, the
more superficial cells of which grow forward as the mesoderm
in a continuous median sheet bifurcating under the cephalic
portion of the ventral plate. We shouid thus have a spot differ-
ing in no essential particular from the caudal plate of Dory-
phora. Jf we suppose that in A/atta the tendency to form the
median groove has become very weak, and is now confined to

No. 2.] BLATTA AND DORYPHORA. 339

the posterior end of the ventral plate, we may regard the de-
pression 4p as the remains of the blastopore. I have remarked
that the gastrula in Doryphora is much deeper posteriorly than
anteriorly, and providing a tendency to obliterate the invagina-
tion should become apparent in an equal degree throughout its
whole length, a short posterior depression like that in A/atta
would be the result. But the opposite possibility, viz.: the
derivation of a gastrula like that of Doryphora from a circular
form like that of A/afta, is likewise worthy of attention. Ac-
cording to Sedgwick (43), the gastrula of Peripatus elongates
with a concomitant closure of the median portion of its orifice.
Of the two openings thus formed the anterior becomes the
mouth while the posterior becomes the anus of the embryo.
Providing a similar stretching of the gastrula has taken place
in the ancestors of Doryphora and Hydrophilus, it would be
easy to see how the cells of the original single Extodermanlage
might be separated to form two masses, which now arise beneath
the stomodzal and proctodzeal area, and how the formation of
the mesoderm from the edge of what was once the gastrula lips
might continue throughout the whole portion of the embryo
between the mouth and anus. If this has been the true
evolutionary process in the development of the elongate gas-
trula of insects, it seems probable that A/atfa may represent

figure 1.— Diagram of germ-layer formation in Doryphora. vp. ventral plate;
og. oral end of gastrula; ag. anal end of gastrula; g. central portion of gastrula; en.
entoderm; e. prolongations of entoderm; aa. plane of cross-section 4; 46. of cross-
section B; cc. of cross-section C; ec. ectoderm of ventral plate; ms. mesoderm.

figure 2.— Diagram of germ layer formation in Blatta (somewhat hypothetical).
Letters the same as in Figure 7.

340 WHEELER. [Vot. III.

the more primitive and Doryphora the more modified method
of germ-layer formation. I would note in this connection that
the mesoderm of A#/at¢ta is formed in a manner strikingly sim-
ilar to that observed in Perzpatus by Kennel (24). Reference
to the diagrams, Figs. 1 and 2, will make further remarks on the
relation of the two modes of germ-layer formation in A/atta and
Doryphora unnecessary.

Kowalevsky, Hatschek, Patten, Heider, and Biitschli have
published observations which have a decided bearing on the
method of entoderm formation in Doryphora.

Kowalevsky (26) claimed in his epoch-making work that in
Hydrophilus the two longitudinal bands of entoderm are derived
by delamination from the splanchnic mesoderm, which he erro-
neously supposed to originate from the primitive mesodermic
layer by an incurling of its lateral edges. As we have seen,
Cholodkovsky also claims that the entoderm of 4/a/za is derived
by delamination from the splanchnic mesodern.

Hatschek (18) figures in Bombyx chrysorrhea a large mass
of entoderm cells immediately beneath the stomodzeum. This
mass may be compared with either the anterior or posterior cell
masses of a similar nature in Doryphora.

Patten (38) figures a cluster of several huge entoderm cells
attached to the stomodzeum of WVeophalax (Pl. XXIV. C. Fig.
36), and in a more recent paper (39) he has figured similar cells
in the same position in the embryo Acz/zus.

Two recent papers on J/usca, one by Kowalevsky (27) and
one by Biitschli (8), contain accounts of a method of entoderm
formation very similar to that observed by me in Doryphora.

Kowalevsky finds that the entoderm originates in two widely
different points, anteriorly at the inner end of the stomodzum
and posteriorly at the inner end of the proctodzum, from some
of the cells of the gastrular invagination. The mass of entoderm
at either of these places forms a watch-glass-shaped body with
its concavity applied to the yolk. From the lateral edges of
each mass the entoderm cells proliferate to form two bands,
each of which unites with the one on the same side growing
from the opposite direction. By a dorsal and ventral growth of
the edges of the two bands the entoderm envelops the yolk and
thus completes the mesenteron. Kowalevsky also regards the
entoderminic invagination in insects as a greatly elongated gas-

No. 2.] BLATTA AND DORYPHORA. 341

trula, which has retained its ability to form entoderm only at the
oral and analends. Putting this construction on the gastrula,
it is, of course, easy to reduce the germ layers of insects to the
Sagttta pattern.

Kowalevsky’s results on JZusca have been corroborated as
far as the posterior Extodermanlage is concerned by Biitschli
(8); while his main results on Hydrophilus have been con-
firmed by Heider (19).

According to Heider, the tube formed by the closing gastrula
flattens out, and the half of it immediately below the ectoderm
becomes mesoderm, afterwards splitting into the somatic and
splanchnic layers; while the other (inner) half becomes the
entoderm which spreads apart to form two bands, one on each
side applied to the part of the mesoderm inclosing the ccelomic
cavity. Subsequently the proliferating edges of the bands
unite ventrally and dorsally to complete the mesenteron.

A comparison of my account of Doryphora with Heider’s
account of Hydrophilus will show that I differ from Heider on
one point only. I claim that all the entoderm between the oral
and caudal widenings of the blastopore is not derived from the
inner cells of the gastrular depression, but grows in from the
ends of the body. I do not deny that the entoderm may arise
in Hydrophilus (and possibly in Doryphora) in the manner
described by Heider, ze. from the inner layer of cells of the
gastrular tube when it flattens out and breaks down, but I
would regard the process as confined to two very small areas,
one being stomodzeal, the other protodzeal.

Heider’s figures are undoubtedly correct and correspond in
every way to sections through Doryphora embryos in corre-
sponding stages. Unfortunately, he has not noted with any
precision the plane of section.of the different preparations
figured. Starting with his Plate II., his figures may be inter-
preted in harmony with Doryphora, thus :—

Figure 23 is exactly like my Fig. 88, omitting the degenerating
nuclei, and I should interpret it in the same way as Heider.
My section passes through the caudal plate of the embryo;
Heider’s passes “durch den Abdominaltheil,’’ which is indefi-
nite. In Figs. 24 and 25 I can see no entoderm, but merely
the apposed splanchnic and somatic layers of mesoderm between
the lateral ends of which the coelomic cavities are about to

342 WHEELER. [Vot. Ill.

form, these cavities being simply enlargements of the at first
very limited space between the two layers at their outer extremi-
ties. Figure 25 is a section through the ‘ Abdominaltheil.”

Both figures accurately represent cross-sections through the
middle of the ventral half of the egg of Doryphora before the
proliferating bands of entoderm have reached the plane of
section (compare my Fig. 78). Heider’s Fig. 26 just skims the
ends of the proliferating bands, showing four entoderm cells at
z beneath the left coelomic cavity in the figure. No portion of
the band was cut on the opposite side, as either the section was
slightly oblique or one of the bands had grown somewhat more
rapidly than the other, a condition which I have often observed
in Doryphora.

The most definite proof that Hydrophilus does not differ from
Doryphora is to be gained from Heider’s own words. He says:
“Wir miissen aber nun auf ein hochst merkwiirdiges Verhalten
eingehen, welches uns beweist, bis zu welchem Grade coenoge-
netische Veranderungen den urspriinglichen Typus der Insecten-
entwicklung entstellen. .Wahrend namlich die geschilderte
Abtrennung des Entoderms von dem unteren Blatte Kowalev-
sky’s im vorderen Theil des Hydrophilus-Embryos (den Kopf-
und Thoraxsegmenten) deutlich zu beobachten ist und ebenso
klar in den letzten Abdominalsegmenten zur Ausbildung
kommt, treffen wir entsprechend den vorderen Segmenten des
Abdomens eine Querzone des Embryos, in welcher keine Ento-
dermchicht zur Anlage kommt—mit anderen Worten: die
Entodermanlage entwickelt sich im Vordertheil und nahe dem
Hinterende des Embryos in zwei gesonderten Stiicken, welche
erst in spateren Stadien gegeneinander wachsen und mit einan-
der verschmelzen. Diese gesonderte Ausbildung des Entoderms
vom Vorder und Hinterende des Embryos ist ein Seitenstiick
zu dem von uns geschilderten und (Taf. L. Fig. 4) abgebildeten,
selbstandigen Auftreten des Vorder-und Hinterendes der rin-
nenformigen Einstiilpung. Wie ich aus den Angaben Kowalev-
sky’s and Grassi’s ersehe, weist das Darmdriisenblatt der Biene
hinsichtlich seiner ersten Anlage ahnliche Verhaltnisse auf.”

b. Embryonic Envelopes.

No phenomenon in the development of the insect embryo is
better suited to call forth conjecture than the embryonic enve-

No. 2.] BLATTA AND DORYPHORA. 343

lopes and the dorsal organ formed soon after their rupture.
For the sake of clearness I shall here consider only the envel-
opes and relegate the discussion of the dorsal organ to my
remarks on the revolution of B/atta and Doryphora at the end
of the next descriptive division of my subject.

Various theories, all more or less vague and intangible, have
been advanced by different investigators to account for the
amnion and serosa. Balfour (2) regarded these membranes as
possibly derived from an early ecdysis. Ayers (1) refuted
Balfour's suggestion; but as he started out in his own explana-
tion with incorrect suppositions regarding the homologies of
the different germ-layers in insects with those of other animals,
he could not fail to involve the amnion and serosa in the gen-
eral error. Kennel (24) regards the embryonic membranes of
insects as homologous with the so-called ‘““amnion” in Perzpatus,
and both structures as the remains of the trochosphere of the
annelid ancestor. Emery (11) suggests that the envelopes may
be homologous with the shell of the Entomostraca.

The question as to the meaning of the envelopes in insects
has been greatly confused by drawing in the widely different
envelopes of Peripatus, Scorpions and Myriopods and the Crus-
tacean dorsal organ, presenting all the different forms observed
in Oniscus, Asellus, Cymothoa, Mysis, etc. Some authors agree
with Kennel in regarding the embryonic envelopes throughout
the Arthropoda as homologues. According to others the dorsal
organs of the Crustacea are the homologues of the amnion and
serosa of hexapods. Still others maintain that the Crustacean
dorsal organ is to be brought into connection with the occasion-
ally similar dorsal organ of insects.

Will (52) has of late advanced a theory to account for the
formation of the embryonic envelopes of insects only. His
theory has the advantage over its precursors in that it replaces
such indefinite terms as “early ecdysis,” “shell of the Entomo-
straca,’ and “Trochosphere” by facts derived from the com-
parative morphology of the membranes themselves. As I came
to essentially the same conclusions as Will long before reading
his article, I may be pardoned for presenting the subject in my
own words, though they repeat in great measure what has
appeared in Will’s paper.

The problem as to the meaning of the amnion and serosa is
restricted to the Hexapoda by postulating the following : —

344 WHEELER. [Vo. III.

1. There are no sufficient reasons for homologizing the
embryonic envelopes of insects with the homonymous but
dissimilar structures in Myriopods, Scorpions, and Perzpatus.

2. There is no more than a superficial resemblance to speak
for an homology between the dorsal organs of the Crustacea and
the embryonic envelopes of Insects or between the dorsal
organs of Crustacea and the homonymous structures in Insects.

3. The dorsal organ of insects may be regarded as the neces-
sary result of the rupture and absorption of the embryonic
envelopes, and consequently as in no way related to such
structures as the dorsal organs of Cymothoa, Limulus, etc.

The process of envelope formation has been observed in
numerous insects of all orders with sufficient accuracy to war-
rant the assertion that all the pronounced types are connected
by intermediate forms in fine gradation ; a fact which was long
ago expressed by Kowalevsky (26).

Diagrammatic longitudinal sections of embryos just after the completion of the
envelopes. igure 3, Geophilus,; Figure 4, Calopteryx,; Figure 5, Aphis; Ligure
6, Doryphora; Figure 7, Blatta; Figure 8, Bombyx. a. amnion; 5S. serosa; @s.
amnion and serosa apposed; wv. ventral plate; fc/. procephalic lobes; y. yolk.

If we suppose such a form as Calopteryx to present the origi-
nal mode of embryo formation in the Hexapoda (and Paleontol-

No. 2.] BLATTA AND DORYPHORA. 345

ogy makes such a supposition probable), we have a form which
will unite readily with an embryo Myriopod in a corresponding
stage of development. In Fig. 3 I have given a diagrammatic
longitudinal section of Geophzlus about the time the appendages
appear. Evidently either the excessive growth in length of the
annelid-like body has necessitated the complete invagination of
the embryo into the yolk, bringing the caudal and cephalic ends
together, or this process has been adopted as a means of bring-
ing the surface of the embryo into more complete contact with
the yolk. It is only necessary to reduce the posterior half of
the infolded embryo (included between 4 and »m in the figure)
to a thin membrane to reach the condition of Ca/opteryx (Fig. 4).
The membrane resulting from the attenuation would be the
amnion. Will has emphasized the fact that the stage with the
amnion almost as thick as the ventral plate with which it is
continuous, still occurs in the ontogeny of insects (compare
Llatta and. Neophalax). He suggests that the attenuation of
the posterior half of an embryo like Geophilus to form the
amnion may account for the great disparity in the number of
segments between the Hexapoda and Myriopoda.

A further difference is observable between Calopteryx and
Geophilus. The end of the original caudal extremity in the
former is joined to the anterior end of the ventral plate, thus
closing the sack whose anterior wall is the ventral plate and
whose posterior wall is the amnion. This sack is attached at
one point to the serosa enveloping the egg. The union of the
membranes to close completely the amniotic cavity is the hinge
about which the further explanation turns.

It seems essential in all the insects so far studied excepting
Musca, where the envelopes are rudimentary, that the amniotic
cavity should be shut off from the space between the vitelline
membrane and the surface of the yolk. The reason for the
closure is apparent if we regard the amniotic cavity as a
place for the temporary deposition of excreted matters, as an
organ functionally analogous to the allantois of higher animals.
It has often been observed that the amniotic cavity of insects
soon after its formation becomes filled with a clear liquid which
during and after revolution is found as a much vacuolated coagu-
lum about the feet of hardened embryos. It seems probable that
while the inner ends of the ventral-plate cells are absorbing and

346 WHEELER. [Vot. III.

metabolizing the yolk, their outer ends are at the same time
giving off into the amniotic cavity a less amount of liquid waste
products. Providing this supposition is true, we should have a
sufficient reason for the constant closure of the amniotic cavity.

We have a complete series of finely graduated forms of enve-
lope formation from the method observed in Calopteryx (Fig. 4)
to Blatta (Fig. 7). Aphis represents the first step in the tran-
sition of an enxtoblastic embryo like Calopteryx to the decidedly
ectoblastic form seen in 4latta. This transition consists in
leaving more and more of the anterior end of the embryo on
the surface of the yolk. In Aphzs (Fig. 5) the whole head is
left outside the invagination; in Doryphora, the head and the
anterior half of the body. When a portion of the embryo is left
on the surface, the closure of the amniotic cavity necessitates a
backward growth of the angle formed by the fore end of the
head and the abutting serosa (as, Fig. 5) to form a fold which
unites with a similar fold formed at the opposite end of the
embryo. In Doryphora, where much of the embryo lies on the
surface of the yolk, the posterior or caudal fold of the amnion
and serosa has to grow forward a considerable distance to meet
the cephalic fold. A/atta has advanced still further than Dory-
phora. The embryo no longer grows into the yolk, but the
formation and ultimate closing of the membranes continues.

At first sight it would seem more natural to suppose that the
result attained in Blatta was brought about simply by an extru-
sion of the yolk between the amnion and serosa of such a form
as Aphis or Calopteryx, but the law of orientation, as explained
in a preceding paragraph, forbids such an interpretation. The
head of the Aphis embryo is at the time of the completion of
the membranes close to the spot before occupied by the caudal
end of the ventral plate, and after revolution the caudal end of
the embryo will again be located at this end of the egg. Hence
the typical ectoblastic originated from the typical entoblastic
embryo, not by an extrusion of the yolk from between the
amnion and serosa, but by a gradual weakening of the invagi-
native process. The weakening, of course, results in more and
more of the anterior portion of the ventral plate remaining inert,
though the growth of the membranes to shut off the amniotic
cavity continues. |

The peculiar free entoblastic embryo observed in Lepidoptera

No. 2.] BLATTA AND DORYPHORA. 347

(Fig. 8) may have originated in two ways: either from a sus-
pended entoblastic embryo like Calopteryx by a separation of
the amnion from the serosa at the point of suspension (Fig. 4 as)
and the consequent passage of yolk between the two membranes,
or from the ectoblastic type of A/atta by a separation of the
amnion from the serosa throughout their area of contact, accom-
panied by an intrusion of yolk. All that we at present know
concerning the formation of the envelopes in Lepidoptera tends
to prove that the latter method is the more probable.

The hypothesis of Will and myself as set forth in the above
paragraphs might be called a mechanical explanation as opposed
to the views of those who see in the embryonic membranes
rudimental structures like the remains of the trocosphere, larval
skins, etc. Our hypothesis has at least the virtue of utilizing
the facts near at hand.

DESCRIPTION OF THE EXTERNAL CHANGES IN THE EMBRYO
BLATTA AND DorRYPHORA UP TO THE TIME OF HATCHING.

Blatta.

Soon after their completion, the amnion and serosa become
more attenuated on account of the flattening of their cells and
the consequent diastasis of their nuclei. This thinning out of
the envelopes permits a better view of the embryo and its form-
ing appendages.

On about the tenth or eleventh day from the beginning of
development, the embryo presents the appearance represented
in Fig. 45. The broadly rounded procephalic lobes are separated
by a deep incision in the median line, and the antennz (a?)
growing from the posterior lateral corners of the lobes have
become prominent, while the backward direction of their growth
is apparent. The labrum (/0) has appeared as a thick, crescen-
tic and slightly divided fold in front of a faint depression
which is the commencement of the stomodzeal invagination. Of
the three pairs of oral appendages, the second and third (sz11, x")
are clearly rounded and directed backwards ; the mandibles are
still small. Each segment of the abdomen presents a pair of
indistinct appendages. These subsequently disappear, with the
exception of the pairs on the basal and terminal segments,
which undergo a differentiation peculiar to themselves, As I

348 WHEELER. (Vor. III.

have given elsewhere (50) a minute account of the pair of appen-
dages belonging to the first abdominal segment, I shall not con-
sider them in the present paper. The pair of appendages belong-
ing to the terminal segment persist and become the anal stylets.
Unlike most Arthropod embryos, the caudal end of the embryo
Blatta (cp!) is never bent dorsally, but from the very early stage
in which it is in a line with the long axis of the abdomen, shows
only a ventral flexure. Owing to this flexure, which soon be-
comes very pronounced, the formation of the protodzeum cannot
be as easily observed as in Doryphora.

The changes which are apparent in surface views by the four-
teenth or fifteenth day have been carefully represented in Figs.
46 and 47. In the former the embryo is zz sztu on the yolk, in
the latter it is isolated and seen from the ventral surface.

As may be indistinctly seen in Fig. 47, the first and second
maxillary appendages have each become split up into three divis-
ions. In @canthus, according to Ayers, “the three oral appen-
dages are trilobed ; the lobation is most prominent in the second
maxillary, and least in the mandibular appendages. The primi-
tive appendage is first divided into two lobes, and the inner of
these becomes secondarily divided into two.” There are appar-
ently no traces of lobation in the mandibles of Alatta. The
outer of the three lobes of each maxilla becomes the palp, while
the inner two become the galea and lacinia of the adult.

fig. 9. Fig. 70. Fig. 77. Fig. 12. Fig. 73.

figure 9.—Embryo of Blatia, 15 days old; revolution about to begin. The
stages in revolution are represented, after the rupture of the amnion and serosa, in
Figures ro-13, which are from embryos 16, 163, 163, and 17 days old respectively.
as. amnion and serosa; s. edge of serosa; J. dorsad growing body wall; d. o. dorsal
organ; «. clear zone covered with scattered amniotic nuclei.

No. 2.] BLATTA AND DORYPHORA. 349

In Blatia the formation of the nervous system in its earlier
stages cannot be clearly seen from the exterior. The same
holds true of the small tracheal invaginations, though several
pairs, especially those of the thorax and basal abdominal rings,
may be seen on the pleuree in good preparations before revolu-
tion. Still they are so much less distinct than in Doryphora
that I have given them little attention.

The peculiar phenomena of revolution are hurried through by
the embryo from the beginning of the sixteenth to the end of
the seventeenth day. Several successive stages in the process
are represented in the woodcuts (Figs. 9 to 13). When fifteen
days old (Fig. 9) the embryo still occupies the middle of the
ventral surface of the egg, the distance from the head to the
cephalic end of the yolk being almost equal to the distance of
the tail from the caudal end of the yolk. The amnion and
serosa (as) still envelop the embryo, though they have become
much attenuated. By the end of the fifteenth or the beginning
of the sixteenth day, the envelopes rupture, an irregular slit
being formed down the median ventral line. The amnion now
appears to undergo degeneration, at least in part, while the
serosa is drawn back from both sides by a contraction of the
protoplasm of its cells, the large nuclei of which make it easy
to trace all the steps in the formation of the dorsal organ.

Soon after the rupture of the envelopes the embryo and egg,
when seen from the side, resemble Fig. 10. The embryo stands
out free from its envelopes on the yolk; the edges of its dorsad
growing walls (4) are distinctly marked. Near these, on the sur-
face of the egg, are seen a number of scattered nuclei, which are
of the same size as the nuclei of the cells forming the embryo.
These I take to belong to the portion of the amnion which has
become folded back on the yolk and forms a zone (7) extending
the whole length of the yolk in contact with the dorsad growing
body wall. Next to this zone lies another zone, which is bounded
by the distinct edge of the serosa (s), and which I regard as a
portion of the yolk left bare, as no nuclei are to be found on its
surface. Besides the ventrodorsal contraction in the substance
of its anterior edge (s), the serosa contracts in an antero-poste-
rior direction, thus producing the constriction seen at y in Fig.
10. The rounded and projecting lump formed at the caudal
pole is the beginning of the dorsal organ (Fig. 10 @. 0). The

350 WHEELER. (Vor. III.

contraction continues towards the median dorsal line and towards
the cephalic pole. In Fig. 11 the dorsal organ has moved half-
way up the dorsal surface. Its darker color in stained embryos
is due to the fact that the serosal cells have become deeply
columnar with a consequent approximation of their large nuclei
to one another. The embryo, besides increasing in size, has
undergone a change in position. Its tail now lies at the caudal
end of the egg. Notwithstanding the embryo’s growth in length,
its head lies much lower than in the preceding stage (Fig. 10).
The body wall (0) is still distinct, the zone of sporadic amni-
otic (?) nuclei (x) has increased in breadth. As in the preceding
stages, these nuclei are most closely aggregated near the edge
of the advancing body wall. In the next stage (Fig. 12) the
dorsal organ has reached the cephalic end of the yolk and bulges
out like a large hood. The body walls of the embryo have
nearly enveloped the yolk at the caudal end.

The next change takes place very rapidly. The stage repre-
sented in Fig. 12 is attained towards the end of the sixteenth
day. By the seventeenth day the walls have closed in the
median dorsal line, and the embryo has grown in length to such
an extent as to bring its head to the cephalic pole. The dorsal
organ has been shut in by, and lies immediately below, that por-
tion of the body wall, which will form the tergum of the pro-
thorax. On entering the yolk the cells of the dorsal organ begin
to disintegrate. Two of the stages in the formation and disso-
lution of the dorsal organ are represented in Figs. 50 and 51,
both from longitudinal sections, the former being sagittal, the
latter frontal.

Figure 50 represents a section through the centre of the thick-
ened mass of serosal cells. The deeply stained nuclei are seen
crowded together in the inner ends of the cells, the contours of
which are rendered papillose apparently by the pressure of the
nuclei against the cell walls. The outer ends of the elongated
columnar cells form a thick layer of granular protoplasm con-
siderably depressed at 0. This depression is equivalent to the
tubular cavity in the dorsal organ of //ydrophilus.

In Fig. 51 the large lump of cells has become engulfed in the
yolk. The body wall has closed over it, and the heart (cc) has
formed between it and the ectoderm. The large deeply staining
nuclei (zz) are seen in the various stages of active degeneration,

No. 2.] BLATTA AND DORYPHORA. 351

many of which recall the degenerating nuclei in the entoderm
of Doryphora. We have the same vacuolization of the karyo-
plasm and agglomeration of the chromatin. In the centre of
the mass a pale, oval spot surrounds an elongated cavity (¢),
which is almost obliterated. This cavity results from the de-
pression o of Fig. 50 by a closing in over it of the peripheral
edges of the dorsal organ.

Figure 48, drawn from an advanced embryo saturated with
clove oil, shows the condition of the different organs shortly
before hatching.. The embryo preserves the shape of the egg,
being much flattened laterally. The segments of the body are
all distinctly defined. The mouth parts have become closely
approximated, and have assumed their definite relations to one
another. The long antennz (a/) extend as far as the two anal
stylets (ast) in which the ventrally bent tip of the abdomen
terminates. The different divisions of the alimentary canal,
cesophagus. (ve), ingluvies (c), proventriculus (gz), stomach (s7),
still containing the remains of the yolk with its degenerating
nuclei, and rectum (7c¢), ending in the anus posteriorly, and
surrounded by a wreath of Malpighian vessels (mpg) anteriorly,
may be readily traced in the figure. The heart is seen as a
delicate tube just beneath the dorsal integument. The large
supracesophageal ganglion (cg/) connected with the large lateral
compound eyes, in which the pigment is being deposited, fills
the greater portion of the brain-box. One of the commissures
is seen connecting it with the infracesophageal ganglion (27%).
The three thoracic ganglia (g/%, ¢/4, ¢/°) are much larger than
the six abdominal ganglia. <A large, granular, fat body (ad) is
applied to the inner surface of pleural wall of the abdomen.
The refractive granules imbedded in it form a chevron in each
of the first five or six somites. Patten (38) in his preliminary
note on A/atta thus describes the physical and chemical nature
of these bodies: “In the embryos of A/azta, as well as in those
of most if not all other insects, there appears in each of the
segments at a certain time a great number of clear, highly
refractive particles that at first might be taken for oil globules,
and which have always been regarded as such. On more care-
ful examination, however, it will readily be seen that this suppo-
sition is incorrect. A number of tests have been made in order
to ascertain the nature of these bodies, and the results show

352 WHEELER. [Vor. III.

that there are some salts of uric acid. That they are not of
a fatty nature is indicated by the fact that treatment of the
embryos with hot benzole, chloroform, or clove oil has not the
slightest effect upon the bodies in question. Further examina-
tion with a high magnifying power shows that they consist of
small spheres of an extremely refractive substance, from the
centre of which dark lines radiate in an irregular manner, pro-
ducing the same appearance seen in the crystals of urea from
the Malpighian vessels. It was this similarity which first sug-
gested the true nature of these bodies; and further tests con-
firmed this view, for, after heating an embryo with nitric acid
upon a glass slide, and then adding a little ammonia, the char-
acteristic red color of Murexid was formed. A still further test
was formed by dissolving the granules in dilute caustic potash,
and then precipitating the urea by adding acetic acid, although
this method did not give such definite results as the first.”

The embryonic development of A/atfa is completed by about
the thirtieth day from oviposition.

Figure 49 shows the embryo soon after hatching. Shortly
after leaving its narrow place in the capsule, the insect under-
goes a peculiar change in shape. While confined by the cho-
rion the diameter from one pleural wall to the other is about
one-third the dorsoventral diameter of the insect. Soon after
hatching, its dorsoventral diameter is only about one-third as
great as its greatest breadth. The tip of the abdomen, ventrally
flexed in the egg, bends dorsally as indicated by the position
of the anal stylets, which now point directly upwards and out-
wards. The spines and onychia, most abundant on the legs,
are developed shortly before hatching.

Doryphora.

Doryphora embryos, when carefully prepared, reveal much
more in surface views than S/atfa embryos prepared according
to the same methods.

The last stage described is represented by Fig. 73. I shall
pass over a few of the succeeding stages, and stop to describe
the embryo represented in Fig. 72, which shows, with great
clearness, all that has taken place in the omitted stages, and
makes a description of them unnecessary. The figure is slightly

No. 2.] BLATTA AND DORYPHORA. 353

diagrammatic, being drawn from a number of different embryos,
each of which contributed some of the details in a clearer and
more pronounced manner. The mouth (9) and anus (a), both
triangular depressions, have become clearly established. The
former has in front of it a heart-shaped prominence, the bilobed
labrum. The lateral half of the head presents some interesting
facts, first elucidated in Patten’s paper on the eyes of Aczlius
(39). Each half of the head is divided by longitudinal constric-
tions into three parallel rounded ridges, each of which is further
divided by two transverse depressions into three subquadran-
gular thickenings. The three inner (61, 2°, 4°) on each side, rep-
resenting the three segments of the brain, are directly continuous
with the ventral ganglion chain, extending to the protodzum.
The row of prominences (ag1, og?, og*) on the outer side of the
three brain segments are the optic ganglion, the further three
(0p', of”, of®), somewhat indistinctly seen because situated on
the very edge of the head, are the divisions of the optic plate,
each of which, in Acz/zus, according to Patten, bears a pair of
ocelli. The only appendages of the head proper in this stage
are the antennz (a¢), which are directed backwards, and the
heart-shaped labrum. The head also presents three pairs of
small invaginations somewhat less distinct than in the figure
(¢1, 22, ¢3). These he near the longitudinal constriction, sepa-
rating the brain thickenings from the thickenings of the optic
ganglion. This is best seen in the third segment, where the
invaginations lie at the bases of the antennz. Following the
third segment of the brain is distinctly seen in some embryos
a short segment inserted between the antennary and mandibular
segments. Its short ganglionic swellings (g/‘) are far apart,
and connected by a broad commissure. This somite may also
have a pair of small invaginations, but I have been unable to
find them. Hereupon follow the mandibular, and the first and
second maxillary segments, each with a pair of invaginations.
Those of the second maxillary segment are concealed behind
the bases of the elongated appendages, but are readily seen in
sections.

The three broad thoracic segments are provided with the
three pairs of legs, all of which are of the same length. The
division into femur, tibia, and tarsus is indistinctly marked. , In
none of the preceding stages have I observed what is so prom-

354 WHEELER. [Vor. III.

inent in #/atta, viz. the appearance of appendages on the
abdominal somites. There are not the slightest traces of even
the pair of appendages of the first abdominal somite, which in
Blatta develop into the large glandular organ of which I have
treated elsewhere (50). The tracheal invaginations are situated
at the bases of the legs. Those of the first thoracic segment
are small, and soon close over and disappear. The second pair,
which are almond-shaped, are the largest in the whole embryo,
and so remain. They are situated near the constriction divid-
ing the first from the second thoracic segment, and in later
stages often have the appearance of belonging to the first seg-
ment. The metathoracic invaginations are somewhat smaller,
and are also placed near the edges of the somite to which they
belong. In the succeeding abdominal segments there is a
tracheal invagination in the middle of each lateral half. These
invaginations become successively smaller till they can be de-
tected only with great difficulty on the 1oth and 11th somites
(¢ 19, 220). The 11th somite is followed by the broad subhex-
agonal caudal plate with its large protodzal invagination. The
corners of the plate are formed by rounded lobes containing
apparently spherical bodies, the ends of the three pairs of Mal-
pighian vessels. These grow off from the protodzum at an
unusually early period in Doryphora, and turn back till their
rounded blind ends terminate just beneath the surface ecto-
derm. The paired ganglionic thickenings are seen in the
embryo figured to be slightly kidney-shaped with their hili
directed laterally. The J/tttelstrang is apparent in the small
and nodular intersegmental thickenings (sz), which appear
from the surface as small masses of cells of a somewhat dif-
ferent nature from those of other portions of the median line.
The surface changes which the embryo undergoes in the
stages immediately following that represented in Fig. 72 may
be briefly summarized. The embryo just described lies like a
band on the ventral yolk, the caudal portion still extending
round the hind pole of the egg, and up the dorsal surface a
short distance. The isochronous changes which ensue are, (1)
a shortening of the embryo, bringing the tail to the pole of the
egg; (2) a broadening of the embryo, the sides of which now
bend dorsally and clasp the yolk; (3) a greater concentration
of the cephalic, mandibular, and maxillary somites to form the

No.2.) BLATTA AND DORYPHORA. 355

head of the larva, and (4) an increase in the length of all the
appendages except the antennz. The shortening of the embryo
stops as soon as its tail reaches the caudal pole of the egg, the
lateral growth of the body continues, and we reach the stage
figured (Fig. 74). The yolk is not yet covered by the dorsad
growing walls of the embryo. The head is distinctly marked
off from the thorax, the wide-spread mouth parts of Fig. 72 have
converged, and are assuming the relations which they bear to
one another in the larva. The ventral nerve chord has devel-
oped considerably, and it is now possible to recognize near the
centre of each ganglion the mass of “ Punktsubstanz”’ definitely
marked off from the cellular portion and united with the corre-
sponding mass of its fellow-ganglion by two-cross commissures.

Figure 75 represents.the larva ready to hatch. The dorsal
body wall has closed, the six ocelli have become pigmented,
the cuticle has developed spines, the meso- and metathoracic
and first abdominal segments have each developed a short,
sharp, black spine in a line with the abdominal spiracles.
These spines are used by the larva in rupturing the chorion,
the vitelline membrane, and the various cuticles which it has
shed before reaching this stage. The movements of the hatch-
ing insect at first produce a rent in the chorion extending from
the first to the third spine, by further struggling the two rents
from opposite sides are made to meet over the head, and the
insect emerges from between the two lips thus formed. The
embryonic development requires about six days.

Before passing on to a description of the internal changes of
Doryphora and Blatta, it is necessary to consider the fate of the
embryonic membranes of the former insect. This is very differ-
ent from what was observed in Blatta. The serosa, instead of
rupturing when the amnion ruptures, separates from it and also
from the entire surface of the yolk, and forms a third egg enve-
lope, beneath the vitelline membrane, to which it applies itself.
It remains clearly recognizable by its large and deeply staining
nuclei till the insect is almost ready to hatch (Fig. 86 s7), when
it disappears, probably by absorption. The fate of the amnion
is peculiar. On rupturing, its two ventrally bent folds turn back
and become in part applied to the yolk. A few of its cells are
loosened from the bulk of the membrane, and are often seen
sticking to the serosa at different points. They are probably

356 WHEELER. (Vo. ITT.

endowed with amoeboid tendencies, for when the ectodermic
wall is about to be completed in the median dorsal line these
cells are seen to have accumulated at the place of closure. The
amniotic cells, which have become applied to the surface of the
yolk by the bending back of the two folds resulting from rup-
ture, have closed in the yolk while the serosa is separating from
it. The advancing body walls of the embryo, however, soon
make the amniotic covering unnecessary, and it contracts in the
median dorsal line to form what may be called an ammnzotic dorsal
organ, to distinguish it from the sevosa/ dorsal organ of latta.
Figure 90 is a part of a section through the median dorsal por-
tion of an embryo in the stage represented in Fig. 74. At do
the protoplasm of the amnion has thickened, and the nuclei are
seen passing in between the yolk bodies. At are a number of
nuclei undergoing degeneration. These resemble the degener-
ating entoderm nuclei to which I have called attention in a much
younger stage. The amnion cells, which have become applied
to the yolk when the membrane ruptures, enter the yolk after
the formation of the dorsal organ by the very narrow slit left
in the closing ectoderm in the median dorsal line. This is seen
somewhat indistinctly in Fig. 85. Nuclei are observed at 6
passing in between the two cardioblasts (cd, cb), which are about
to meet and form the heart. The splanchnic mesoderm (s/w),
with the underlying entoderm, still leaves a wide gap through
which the migration into the yolk takes place. The granular
matter surrounding the nuclei is probably the remains of the
cytoplasm of the amnion cells. In the figure a number of entire

Figures 14-16.— Three diagrammatic median cross-sections through the egg of
Doryphora, before and during revolution. ch. chorion; v. vitelline membrane, ap-
plied to the inner face of the chorion; @. amnion; s. serosa; e#. embryo; do. dor-
sal organ (amniotic); y. yolk.

No. 2.] BLATTA AND DORYPHORA. Lvs

amnion cells (a) are still seen just beneath the serosa, and one
is seen right at the narrow space between the cardioblasts. The
last steps in the process are represented in Fig. 93. The dorsal
ectoderm has become continuous at ec¢ in the median line. The
two cardioblasts are still in the same stage. One of the last
amnion nuclei is passing in surrounded by a mass of granules.
A clear idea of the revolution of the embryo Doryphora may be
obtained from the three stages in the diagrams.

The method of revolution just described is very similar to that
observed by Graber (15) in Zzza. Though he did not give a
description of the complete process, he made the important
observation that the serosa remains unchanged till after the chite-
nous cuticle 1s formed.

GENERAL REMARKS.
Dorsal Organ.

The term “dorsal organ’’ has been applied to the peculiar
thick lump of cells resulting from the concentration on the dor-
sal yolk of the remains of either the amnion or serosa, or of both,
preparatory to their sinking into the yolk and being absorbed.

A similarity in form and position has led many investigators
to look for an homology between the dorsal organ of insects and
the homonymous organ of the Crustacea.

My observations on the dorsal organ of Cymothoa have con-
vinced me that there are fundamental differences between the
Crustacean and Hexapod dorsal organ. First, the dorsal organ
of this form, and probably other Isopoda, is a structure which
persists from an early stage almost to hatching, and may persist
throughout life in some Branchiopoda, whereas the dorsal organ
of insects is a very transitory structure. Secondly, the dorsal
organ of Cymothoa seems to be a secretory organ, as was deemed
probable by Balfour (2). I have observed that the elongated
cells which form the organ secrete a reniform sack of chitin,
which is joined by means of a corrugated chitinous tube to the
cuticle shed from the surface of the embryo at a very early
stage. Nusbaum (34) has observed that the cavities of the
dorsal organs of J7yszs are filled with a clear substance, probably
a secretion.

The presence of the so-called dorsal organ in insects is prob-

358 WHEELER. [Vot. III.

ably due to the fact that the embryonic envelopes are to be
absorbed. As these membranes consist of assimilable matter,
it is obviously an advantage to the embryo to be able to add
them to the stock of food represented by the yolk. The simplest
conceivable method of effecting the resolution of the envelopes
into food material, considering their position when fully devel-
oped, would, of course, be to engulf them in the yolk, where,
under the influence of the yolk cells, metabolism is being
actively carried on. There are two methods of inclosing the
membranes in the yolk. According to one, they might undergo
dissolution zz situ, according to the other, they might be
brought together in a mass and swallowed up by the yolk some-
where in the median dorsal line. Obviously the latter method
is the more advantageous, as the body walls, continually grow-
ing towards the median dorsal line, might be impeded in their
advance if the membranes were absorbed at all points on the
surface of the yolk. Probably the inconvenience which would
thus result from a diffuse absorption accounts for the fact that
it does not occur, though a modification of the method occurs
in Doryphora, where the serosa is absorbed very late in develop-
ment after the larva has secreted its second cuticle and is almost
ready to leave the egg.

Given a thickening, somewhat flattened mass of cells, des-
tined to be swallowed up in the yolk, and it is most natural to
suppose that the organ, in passing into the yolk, would become
cup-shaped as in A/azta, or form a thick-walled tube, if the organ
extended the full length of the dorsum, as in Hydrophilus. In
either case the outer ends would be made to converge, by the
lateral pressure of the yolk and the sinking of the median por-
tion of the organ, and we should get a closed tube or sack. This
would not, of course, hold true of an organ formed like the
amniotic dorsal organ of Doryphora, for the reason that in this
case the decomposition begins as soon as the organ is formed,
and not after it has passed into the yolk, as is the case with
the serosal dorsal organs of other forms (//ydrophilus, Blatta,
Neophalax). Hence the cavity of the Hexapod dorsal organ
would resemble the cavity or so-called micropyle of the Isopod
dorsal organ, though the two cavities would not be homologous.

No. 2.] BLATTA AND DORYPHORA. 359

THE FATE OF THE DIFFERENT GERM LAYERS.
A. Entoderm.

Recent writers on insect embryology have recognized two
forms of entoderm,—one called primary, and represented by
the yolk cells; and one secondary, represented by the’ epithe-
lial wall of the mesenteron. In A/atza the yolk nuclei steadily
increase in size from their first appearance at a time when they
are no larger than other nuclei. At the time of the formation
of the dorsal organ they are by far the largest nuclei in the egg
(Fig. 51 v). Their chromatin is distributed through the karyo-
plasm in the form of a fine, convoluted thread, and as two
or more nucleoli (Fig. 54 v). Soon after the closing-in of the
yolk, they lose their rounded outline, and become irregular and
more homogeneous (Fig. 55 v). In the last stages of their
dissolution they may be seen as stellate spots in the remains of
the yolk aggregated in the stomach of the advanced embryo
(Fig. 48). Yolk segmentation, though occurring in A/azza, takes
place after the appendages are formed, at a much later period
than in Doryphora. The segments, usually very obscurely de-
fined, become confluent again as development continues.

In Doryphora the yoke cells undergo no increase in size from
the time of their first appearance ; but soon after the yolk has
become segmented their cytoplasm is reduced to a scarcely
perceptible layer surrounding the nucleus, which has become
irregularly polygonal (Fig. 83). As all the eggs I studied were
killed and preserved in the same manner, this difference in
form between the yolk nuclei in the stages during yolk seg-
mentation and after this process till the setting-in of degenera-
tion, must be regarded either as a normal change in the living
nuclei, or as indicating that their chemical nature is changed,
and their resistance to the altering effects of reagents lessened.

After the completion of the mesenteron at a time when the
larva is almost ready to hatch, the remains of the yolk nuclei
are pushed back into the stomach in the same way as in Blatza.
Here they degenerate in a manner very similar to that observed
in the secondary entoderm nuclei, and the nuclei of the amniotic
dorsal organ. They become swollen and vesicular, and their
chromatin is reduced to irregular masses. The yolk becomes a
compact, granular mass, staining pink in borax carmine.

360 WHEELER. [Von. IIT.

The origin of the secondary entoderm in Doryphora has been
treated of at length in preceding paragraphs. We have now to
trace its fate, from the condition in which we left it, as two
masses, — one under the blind end of the cesophagus, and the
other under the blind end of the proctodeum. In an embryo
of the stage of Fig. 72, each of the isolated masses has begun
to send out the two bands of entoderm. These diverge from
their point of origin, and apply themselves to what is to be the
splanchnic mesoderm (Fig. 78 ex¢). Their divarication is so
slight that a thick longitudinal section will sometimes include
a whole band, if still short. Thus, in Fig. 92, from a section
through an embryo in the stage of Fig. 72; passed to one side
of the median line, we have the entoderm (ev) still attached to
the mesoderm (msd), which is now distinctly marked off from
the ectoderm of the stomodzeal invagination (s¢). The entoderm
is attached to the inner end of the cesophagus, and extends
along the yolk as a band two or three cells thick. It is clearly
distinguishable from the mesoderm by the greater clearness of
its cells, and by its paler nuclei. The process at the posterior
end of the embryo is similar, as may be concluded from Fig.
76, from the same embryo. Like the anterior thickening, the
posterior mass does not remain stationary, but grows out in two
bands. Thus it happens that little entoderm is found right
under the proctodeum. The knife has not passed through the
proctodzal invagination in the figure, but has cut to one side
of the median line, through the Malpighian vessels mpg! and
mpg” of Fig. 72. The true relations of these vessels may be
understood from an examination of Fig. 77, and the present
section, Fig. 76. The strand of entoderm, very similar to the
anterior strand described above, is attached to the proctodzeal
pocket near the point at which one of the first pair of Mal-
pighian tubes (#pg") turns out toward the surface of the embryo,
pushing aside the mesoderm, which elsewhere forms a continuous
sheet under the ectoderm.

In the same figure may be noticed a second mass of entoderm
(ent) attached to the proctodzum near the point at which the
third pair of Malpighian tubes branches off from the common
proctodzeal pocket. This mass ends with a sharp point between
two yolk segments. I have seen similar masses of entoderm in
a few other embryos, apparently independent of the two main

’

No. 2.] BLATTA AND DORYPHORA. 361

forward-growing strands, and terminating in the same acute
point which seems to force its way between the yolk segments.
These points of entoderm do not grow far, as I have concluded
from an examination of slightly older stages, but soon fuse with
the bases of the two main strands, and form a meniscoid mass
in every way comparable with the watch-glass-shaped mass in
Musca, as described by Kowalevsky (27).

A median cross-section of an embryo, with the entoderm
bands fully established, but not confluent, is shown in Fig. 78.
The embryo is cut in two places. The upper half passes through
one of the basal abdominal segments, while the lower half passes
through the abdomen, a short distance from the tail. In the
upper half no entoderm cells are to be found, as the two bands
have not yet reached in their forward growth the basal abdominal
segments in which they fuse with the two bands growing back
from the stomodzal invagination. In the lower half a heap of
succulent entoderm cells is seen on each side, separated from
the coelomic cavity (c/) by the splanchnic mesoderm (s/).

Four stages in the formation of the mesenteron after the
establishment of the entoderm as two long bands, are repre-
sented in Figs. 83 to 86 ext. The entoderm remains throughout
embryonic development perfectly distinct from the splanchnic
mesoderm, to which it is nevertheless very closely applied. At
first the cells are irregularly arranged in the band which is
deepest in the middle, but gradually flattens out to a single cell
in thickness at its dorsal and ventral edges (Fig. 83). In a later
stage, however, the nuclei have their long axes directed at right
angles to the long axes of the splanchnic mesoderm cells (Fig.
84), and thus indicate that the cells of the entoderm are begin-
ning to assume a definite columnar arrangement, though they
still lie, in some places, in two or more rows, one above the
other. By the time the body walls are about to close, the cells
of the entoderm have formed an even layer of columnar ele-
ments (Fig. 85), an arrangement which is retained in all the
subsequent stages till the embryo hatches.

The growth of the entoderm, accompanying the adjacent
mesoderm and ectoderm in their dorsad movement, is at first
largely along the dorsal edges of the bands, as may be seen by
comparing Figs. 84 and 85, where the distance between the
ventral edges of the two bands is nearly the same, while the

362 WHEELER. [Vou. III.

distance between the dorsal edges is greatly lessened. The
transformation of the original ribbon of several superimposed
rows of cells into the simple epithelium of columnar cells is not
entirely due to cell division. As may be seen from Figs. 84
and 85, either the wandering of the inner rows of cells over the
outer towards the dorsal edge of the ribbon, or a stretching of
the whole band, so as to permit an intercalation of the cells
of the inner rows between those of the outer row, are the more
probable factors in the thinning out of the entoderm. The
latter method is more probable, though the former method is
certainly in keeping with the gliding and mobile movements of
the entoderm. The nuclei of the entoderm have their chromatin
distributed in the typical filament, which is more attenuated
than in either mesoderm or ectoderm nuclei. Shortly before
hatching the chromatin of the mesenteron nuclei appears to
have dissolved, as they seem to have become perfectly homo-
geneous, though they still stain deeply. In the hatching larva
the cells have become more deeply columnar, on account of a
diminution in calibre of the mesenteron. The nuclei cease to
absorb more of the staining fluid from the surrounding cyto-
plasm, though the walls retain their evenly rounded contour.
Such a fundamental change in the nuclei would seem to indicate
that some important change is about to take place in the mes-
enteric layer of cells; but whether this change is dissolution I
am unable to say, as I have not studied the insect in the stages
beyond hatching.

The process of mesenteron formation is essentially the same
in Blatta as that just described for Doryphora. From the first,
the entoderm cells of 4/a¢ta are as small and indistinct as the
yolk cells are large and prominent. They form, as stated above,
two bands of very flat cells bearing the same relations to the
mesoderm as the corresponding bands of Doryphora (Fig. 54
ent). The edges of the two ribbons continue their growth, and
meet ventrally and dorsally, to complete the mesenteron (Fig.
55 ent).

Besides the lining of the mesenteron the corpus adiposum,
represented during the embryonic life of Doryphora by a number
of granular cells which constantly increase in size up to the time
of hatching, probably originates from the entoderm. I have
observed in several cases that before the two posterior bands of

No. 2.] BLATTA AND DORYVPHORA. 363

entoderm have reached the middle of the embryo a number of
granular and somewhat larger cells are to be found mingled with
the cells of the bands. I conclude that these cells are of ento-
dermic origin because when first seen they are associated with
the entoderm cells and resemble them more closely than they
resemble the adjacent mesodermic elements. At first small
(Fig. 85 ad), these fat cells gradually but constantly increase in
size, their cytoplasm and nuclei increasing in about the same
ratio. They wander about in the body cavity, but finally attach
themselves to the ectodermic body walls, especially in the pos-
terior two-thirds of the embryo on each side of the heart (Fig.
86 ad). They remain more or less globular or oval, the side in
contact with the wall hollowing out a concavity in the cells of
the ectoderm. The granulation of the cytoplasm which first
distinguishes the fat cells from the true entodermic elements
becomes coarser with the increase in volume. In the embryo
ready to hatch the adipose cells have acquired gigantic dimen-
sions, being many times the size of those represented in Fig. 86.
Both nuclei and cytoplasm stain deeply, so that these fat cells
are rendered among the most conspicuous objects in a section.

B. Mesoderm.

In Doryphora as soon as the gastrular tube has collapsed, the
polygonal mesodermic elements form a layer several cells in
thickness, applied to the inner surface of the median ventral
ectoderm (Fig. 65 msd). This layer of cells thins out at its
lateral edges. With the first traces of segmentation in the outer
layer the mesodermic layer also divides, though incompletely, at
the same places of constriction (Fig. 82). Soon the single
intersegmentally divided band of mesoderm splits in the median
line so that each segment contains two subquadrangular flat-
tened masses. The ccelomic cavity is formed at the outer
edge of each of the masses by a separation of the cells of the
two layers (Fig. 78 c/). The inner constitutes the splanchnic
mesoderm, while all the remainder of the mesoderm constitutes
the somatic layer (Fig. 78 s/m). When the appendages appear,
it is the latter layer of cells which supplies their cavities with
muscle-forming cells; the portions inclosing the ccelomic cavity
accompany the adjacent ectoderm in its dorsad growth. As

364 WHEELER. (Vor. Ii.

soon as the growth in this direction is fairly started the ecto-
derm bulges out (Fig. 83 ect) and, drawing with it the somatic
mesoderm, leaves a cavity between the yolk and the embryo
which soon communicates with the coelomic cavity and assumes
large dimensions (Fig. 84). Through the body cavity thus
formed a thin plasma found as coagulated masses in hardened
embryos probably circulates.

The cell cd (Fig. 83), which is recognized even at a much
earlier stage by its peculiar form, and which is destined to take
part in the formation of the heart, is the only element still
uniting the splanchnic and somatic layers. This cell, as may be
clearly seen in Figs. 83 and 84 cé, is triangular in cross-section,
and inserts one of its acute angles between the yolk and the
ectoderm. As this cell with those of exactly the same shape
anterior and posterior toit form the heart, I shall call it a cardio-
blast. The true shape of the cardioblasts may be seen ina thick
frontal section (Fig. 89) through the embryo of which Fig. 84 is
a cross-section. Here the compact row of crowded but regular
heart-forming elements (cd) is seen running between the actively
proliferating entoderm cells (ez¢) on the one hand, and the meso-
derm cells (#zsd@) on the other. These last are somewhat scat-
tered in the space between the cardioblasts and the thickened
ectoderm.

In the more advanced embryo (Fig. 85) the cardioblasts (cd)
from either side are near together. They have retained their
characteristic form and position, while the somatic mesoderm
has been converted into muscles (#s/) and connective tissue,
and the splanchnic layer (s/vz) has applied itself closely to and
is coextensive with the single-celled layer of entoderm (e772).
In Fig. 86 the heart is completed. A glance at this figure and
Fig. 85 shows the manner in which the two cells from opposite
sides unite. Though forming the two halves of the tube in
Fig. 86, they still show the three angles which were apparent
just after the formation of the ccelomic cavity. The heart
remains in the condition shown in Fig. 86 till the embryo
hatches. I have not studied the formation of the blood in
Doryphora.

My observation on the formation of the sexual organs, though
more complete than in 4/a/za, are still very fragmentary. These
organs originate as two elongate thickenings of splanchnic

No. 2.] BLATTA AND DORYPHORA. 365

mesoderm, one on each side projecting into the body cavity.
Later (Fig. 84 gz) they become rounded and are attached by a
thin band of splanchnic mesoderm only. I have seen the much
attenuated duct leading from each organ to the exterior, but
have made no observations on its origin. The ducts converge
posteriorly, but end by separate openings on the 11th abdominal
somite; thus presenting a condition which in Ephemerids is
permanent throughout life, according to Palmén (37). There
is probably some connection between the two pairs of very
indistinct tracheal openings in the 1oth and 11th somites and
the openings of the efferent ducts, but I was unable to deter-
mine whether the large sexual openings originate by enlarge-
ment from a single pair of these tracheal openings, or from the
confluence of all four to form two orifices. The cross-section
(Fig. 80) includes the openings of the efferent ducts (go go), the
knife having taken away a very thin layer of surface cells.

Up to the formation of the coelomic cavities the mesoderm of
Blatta closely resembles the same layer in Dorvyphora. With
the evagination of the appendages from the entoderm a decided
difference is, however, observable. Each coelomic segment, if
situated in an appendage-bearing segment, instead of retreating
dorsally as in Doryphora, sends a diverticulum into the appen-
dage. This is clearly seen in Fig. 53 c/, a cross-section from an
embryo twelve days old. The cells of the diverticulum develop
into the muscles of the appendage, and together with a portion of
the mesodermic layer still remaining in the body cavity are shut
off from what probably represents the true coelomic cavity (Fig.
54 c/). The further changes again resemble those in Doryphora.
Long before the heart is formed and the lateral walls have met
in the median line, the body walls of the embryo are observed
to pulsate regularly like the body walls of Gryllotalpa, as
described by Korotneff (25). As in Doryphora a plasma is at
this time found in the body cavity which is divided by films of
connective tissue into a great number of small intercommunicat-
ing lacunz (Fig. 54). In regard to the primitive blood sinus,
my observations confirm Patten’s (38). He says: “The primitive
blood sinus is the space between the somatic and splanchnic
mesoderm, divided into a number of smaller and irregular
sinuses by meshes of connective tissue, some cells of which, in
the earlier stages, become free and form the blood capsules. By

366 WHEELER. (Vor. III.

the pulsation of the mesodermic folds, long before a special
heart is formed, a circulation through the body cavity is
brought about like the circulation in many of the lower worms.”’

One of the stages in the formation of the heart is seen in Fig.
52. The cardioblasts (cé cb) are both more numerous and more
irregular than in Doryphora. They unite to form a tube, the
lumen of which is at first oblong in cross-section (Fig. 52 %).
In the cardiac walls amoeboid cells are occasionally seen (07),
which loosen themselves from the mesodermic elements and
pass into the lumen of the tube, probably to form blood cor-
puscles.

C. Ectoderm.

My observations on the organs derived from the ectoderm are
limited almost exclusively to Doryphora.

The hypodermis of the embryo secretes two cuticles, the
second of which covers the larva, while the first is cast off at
the time of hatching. Shortly before hatching the embryo is
confined by four loose envelopes, —the chorion, the vitelline
membrane, the serosa, and the first cuticle. Graber (15) has
made a similar observation on the embryo Lzma.

The three broad-based chitinous spines used by the insect in
rupturing its envelopes, and which are analogous to the frontal
spine observed in Stvongylosoma by Metschnikow (31) and the
deciduous claw on the beaks of birds, are secreted by pyramidal
thickenings of the hypodermis (Fig. 86 sf), the cells of which
are much lengthened, though forming a single layer.

In the surface views of the embryo (Fig. 72) it is possible to
trace the origin of all the ganglia as paired thickenings of the
outer layer. At first these thickenings differ histologically in
no particular from the surrounding ectoderm (Fig. 78 77).
Gradually, however, the cells in the centre of each thickening
enlarge, while their cytoplasm becomes drawn out into fine
threads. At the same time all the ganglion cells thus formed
arrange themselves in such a way as to have their threads inter-
mingle. Zhzs mass of intertwined threads becomes the Punktsub-
stanz (Fig. 94 to 104 pct). The outer layer of cells (e) contin-
uous with the hypodermis (ecd’) stands off somewhat from the
ganglionic thickenings, leaving a space which is in early stages
occupied by several large, clear, oval cells (gé/), which divide

No. 2.] BLATTA AND DORYPHORA. 367

rapidly by karyokinesis, and might be called ganglioblasts, as the
products of their divisions reinforce the mass of ganglion cells.
In a series of sections through the mesothoracic pair of ganglia
(Figs. 94 to 104) the Mittlestrang may be readily traced. The
shape of its cross-section varies with the plane of section
through the ganglion and its cross or longitudinal commis-
sures. At the two points in the ganglion where the two pairs
of Punktsubstanz masses fuse to form the commissures c cm, the
Mittlestrang is in great part obliterated. The median strand is
largest where the two longitudinal commissures are passing into
the anterior ends of the three thoracic ganglia. Here they
persist in the larva, while completely disappearing elsewhere,
and become converted into the three chitinous furce, cach one of
which ws gust in front of a thoracic ganglion.

Figure 105, from a section through the fore end of the meta-
thoracic ganglion, shows the Mittlestrang portion (#s¢) contin-
uous with the hypodermis (ect) and broadening out into the
furca (f) after passing between the two halves of the ganglion
(g7). Muscles (m#s/) are attached to the two divergent ends.
The mesothoracic furca, which is formed in exactly the same
manner, is seen in Fig. 86 f, where it passes between the
commissures (cw); its connection with the muscles is seen
ENE

A frontal section (Fig. 91) shows the structure of the meso-
and meta-thoracic ganglia after they have become loosened from
the surface ectoderm. The longitudinal (cz) and cross-com-
missures (¢ cm) are clearly seen as white Punktsubstanz sepa-
rated from the ganglionic cells by the inner neurilemma (2777).
The outer neurilemma (0777) is also developed, as are also the
two main nerve trunks (z!}, 2”), the anterior of which bifurcates
(z) while leaving the ganglion.

The separation of the nervous system from the integumen-
tary ectoderm progresses from before backwards. The two
brain masses separate first. The first segment becomes very
small and possibly disappears. The three segments of the
optic ganglion are invaginated and pushed under the optic
plate in a manner which I believe to be similar to that de-
scribed by Patten (39) in Aczdzus, though I have not followed
the details of the process. The frontal ganglion is formed as an
unpaired thickening of the dorsal wall of the wsophageal ecto-

368 WHEELER. [ VoL. III.

derm near the base of the labrum. Punktsubstanz is formed in
this ganglion in the same manner as in the brain and ventral
ganglia. It is ultimately loosened from the stomodzeum, and
becomes surrounded by mesodermic elements. Later the four
pairs of ganglia of the intercalary, mandibular, Ist and 2d max-
illary segments fuse and form the infracesophageal ganglion.

That the outer neurilemma is of ectodermic and not of meso-
dermic origin seems to be proved by the fact that shortly after the
separation of the nerve-chord from the integumentary ectoderm, tt
sheds from its surface a delicate chitinous cuticle stmultaneously
with the shedding of the first integumentary cuticle. This cuticle,
which is separated from the surface of the outer neurilemma, and
even from the surfaces of the main neural trunks, is afterwards
absorbed.

The six ocelli are formed as apple-shaped thickenings of the
optic plate. Their small size has hindered me from studying
their structure in detail. I have represented in Fig. 81, soon
after their first appearance, two of the ocelli corresponding to
the eyes of Aczlzws numbered V. and VI. by Patten. Each
forms a slight depression somewhat paler than the surrounding
ectoderm. The nucleus (7) of one of the central cells is seen
to be much larger than the nuclei of the surrounding cells.
Patten has described and figured this same large nucleus in the
éyes or Actus (Pl. XI., Figs: 63, 64, 65; etc.).

The five pairs of invaginations anterior to those of the second
maxillary segment form the tentorium of the larval head. These
invaginations grow inwards:-as slender tubes, which anastomose
in some places. Their lumina are ultimately filled with chitin.
Palmén (36) found that the tentorium of Lphemerids breaks
across the middle during ecdysis, and that each half is drawn
out of the head, like the chitinous lining of a tracheal tube.
This fact, together with my observations on the tentorium of
Doryphora, makes it highly probable that, as Palmén suggests,
the tentorium is formed from trachez, which have become
modified for muscular attachment.

Of the true tracheal invaginations, those of the pro- and
meta-thorax disappear. The mesothoracic spiracle comes to lie
between the pro- and meso-thoracic segments near the base of
the legs and ventral to the line of abdominal spiracles. This
first spiracle is the largest, and in cross-section appears as a

No. 2.] BLATTA AND DORYPHORA. 369

short, chitinous cylinder, projecting somewhat from the general
surface of the segment. Its inner walls are lined with spines
which are directed outward. The abdominal spiracles, though
smaller, are also lined with similar spines (Fig. 85 ¢v). The first
pair of tracheze send large branches to the head. The abdominal
trachez of each side of the body anastomose to form a longi-
tudinal trunk, from which the branches ramify to the different
organs. The invaginated ectodern, at first very thick (Fig. 84
tr), gradually thins out as the respiratory tubes lengthen and
ramify. The thin epithelium thus formed secretes the chitinous
lining provided at the time of hatching with the spiral thicken-
ings so characteristic of insect trachez.

The proctodzum and stomodzum when first formed are tri-
angular in cross-section. Later both become hexagonal (Figs.
79 and 80). A like pronounced similarity in form between the
stomodzeum and proctodzum of Gammarus has been observed
by Pereyaslawzewa (40). She says: ‘Fait tres intéressant, qui
mérite d’étre noté, c’est qu’a mesure de l’acroissement du rectum
et de l’cesophage, leur partie intérieure affecte absolument la
-méme forme carrée, dont les parois sont concaves. Ce qui
concerne la configuration des cavités, elles n’en différent aucune-
ment et se dessinent sous forme d’une croix oblique; la dis-
semblance consiste en ce que dans Vcesophange ce sont les
parois qui s’enfoncent, tandis que les parois du rectum sont
tapissés d’un epithelium cylindrique, dont les cellules s’aplatis-
sent graduellement vers les angles.”

The three pairs of Malpighian vessels appear at a very early
period, while the proctodzeal invagination is still very shallow.
They are from the first hollow diverticula, and have their blind
ends pushed back by the forward growth of the proctodzum.
Thus it happens that a transverse section through the tail-end
of an embryo in the stage of Fig. 74 passes through both the
proctodzeum and the Malpighian vessels (Fig. 79, 7, mpg, mpg).
When the blind ends of the six tubes have struck the body wall,
their continued growth forces them to turn and grow forward.
After the formation of the dorsal body wall, they may be found
lying as thin undulating tubes, surrounding the mesenteron at
approximately equal distances from one another (Fig. 86 mg).

The very early appearance of the Malpighian vessels and
their paired arrangement in Doryphora, Fig. 72, would seem to

370 WHEELER. [Vot. Ill.
indicate that at one time they opened on the surface of the
body, and that their orifices were subsequently carried in by a
deepening of the proctodzal invagination. Possibly these tubes
in insects are homologous with the anal tubes of the Echzurus
larva, which are modified segmental organs. Gegenbauer (14)
has intimated the possible derivation of the Malpighian vessels
from paired tubes opening on the outer surface of the body.
He says: “As they [the Malpighian vessels] are formed at
the same time as that portion of the hind-gut, which in the
embryo is developed from the ectoderm, it is not improbable
that they primitively opened on the surface of the body, or were
derived from organs which did so. In all divisions there are
two chief canals, as is often seen at the point where a large
number of canals open and unite. This number may therefore
be regarded as a primitive character.”

MILWAUKEE, Sept. 12, 1888.

LIST, OF WORKS REFERRED) TO:

1. Ayers, H. On the development of CGécanthus niveus and its Parasite
Teleas. Memoir. Boston Soc. Nat. Hist. Vol. III., No. 8. 1884.

2. Balfour, F. Treatise on Comparative Embryology. Vol. II]. 1881.

3. Blochmann, F. Ueber eine Metamorphose der Kerne in den Ovarial-
elern und iiber den Beginn der Blastodermbildung bei den Ameisen.
Verhand d. naturh. medicin. Vereins zu Heidelberg. Bd. III. Heft
3. 1884.

4. Blochmann, F. Ueber die Reifung der Eier bei Ameisen und Wespen.
Festschrift zur Feier des 100 jahr. Bestehens der Ruperto-Carola.
Heidelberg. 1886.

5- Blochmann, F. Ueber die Richtungsk6érperchen bei Insekteneiern.
Morph. Jahrb. Bd. XII. Heft 4. 1887.

6. Brandt, A. Ueber die Eirdhren der Blatta (Periplaneta) orientalis.
Mém. Acad. St. Petersbourg. Sér.7. Tom. XXI. 1874.

7. Bruce, A. T. Observations on the Embryology of Insects and Arachnids.
Baltimore, 1887.

8. Biitschli,O. Bemerkungen iiber die Entwicklungsgeschichte von Musca.
Morph. Jahrb. Bd. XIV. Heft 1. 1888.

g. Carnoy, J.B. La Cytodiérése chez les Arthopodes. ‘‘ La Cellule.” Tom.
I. Fasc. II. 1885.

10. Cholodkovsky, N. Ueber die Bildung des Entoderms bei Blatta ger-
manica. Zoolog. Anzeig. No. 275. 1888.

11. Emery, C. (Critical note on Korotneff and Grassi) Biolog. Centralbl.
Bd. V. 1887.

No. 2.] BLATTA AND DORYPHORA. 371

oe
13.

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16.

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22:
236

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pip

Flemming, W. Zellsubstanz, Kern u. Zelltheilung. Leipzig, 1882.

Flemming, W. Neue Beitrage zur Kenntniss der Zelle. Arch. f. mikr.
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Gegenbauer, C. Elements of Comparative Anatomy. Trans. by F.
Jeffrey Bell. London, 1878.

Graber, V. Die Insekten. II. Theil. Miinchen, 1877.

Graber, V. Ueber die primare Segmentirung des Keimstreifs der In-
sekten. Morph. Jahrb. Bd. XIV. Heft 2. 1888.

Hallez, P. Loi de l’orientation de l’embryon chez les Insects. Compt.
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Hatschek, B. Beitrage zur Entwicklungsgeschichte der Lepidopteren.
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Heider, K. Ueber die Anlage der Keimblatter von Hydrophilus piceus.
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Henking, H. Untersuchungen iiber die Entwicklung der Phalangiden.
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der Zellen? Jena, 1884.

Huxley, T. A. Manual of the Anatomy of Invertebrated Animals. 1878.

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Bas4r. Heft 4. 1s5:

Kowalevski, A. Embryologische Studien an Wiirmern u. Arthropoden.
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37:

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48.

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52.

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Ate) ett 3. 1885.

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Bd. III. Heft 2. 1888.

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374 WHEELER.

DESCRIPTION OF PLATE XV.

Blatta germanica.

Fic. 1. Piece of chorion from lateral face of odthecai egg.

Fic. 2. Piece of chorion from micropylar area with micropyles. @, aperture of
micropyle; 2, tubule.

Fic. 3. Transverse section through the crista of a capsule. 0, odthecal wall split-
ting into two laminze, 0! and 0; cv, crystals of calcium oxalate; ef, remains of fol-
licular epithelium.

Fic. 4. Longitudinal section of epithelial cap on the germarium pole of the egg.
ef, follicular epithelium; c#, chorion secreted by the same; a, the point at which the
chorion widens, showing its lengthened trabeculz; 4, pyriform dilatation of the chorion;
pr, protoplasm of the Keinhaut, containing numerous bacteria-like corpuscles.

Fic. 5. A number of cells from the follicular epithelium. a, resting nucleus; 4
and ¢, nuclei in akinetic division.

Fic. 6. Longitudinal section of immature ovum I mm. long, being the circum-
nuclear portion in the centre of the dorsal concavity of the egg; nucleus amoeboid
just after reaching the surface. , chromatin particles; x, layer of small yolk bodies
just beneath the epithelium.

Fic. 7. Same section of an egg 2mm.long. Nucleus emarginate on outer surface,
giving off the maturation sphere 4; y, small yolk bodies under the epithelium.

Fic. 8. Section at right angles to that in Fig. 7, of a nucleus in the same stage.
6, cavity into which the maturation spheres fitted; #72, paranucleolus.

Fic. 9. Nucleus in the same stage; fz, paranucleolus. Egg 2 mm. long; section
in the same plane as Fig. 7.

Fic. 10. Longitudinal section of median dorsal surface of an egg 2.5 mm. long.
Particles of chromatin aggregating into a somewhat stellate central mass.

Fic. 11. Longitudinal section corresponding to Fig. 10 of an egg somewhat older,
2.8 mm. long. A delicate wall encloses the particles of chromatin. ;

Fic. 12. First polar spindle in the metakinetic stage. Egg mature.

Fic. 13. First polar spindle in anaphasis. Egg mature.

Fic. 14. Median longitudinal section through the dorsal surface of an oédthecal
egg 4 to 6 hours old. /g/, first polar globule; «, second polar spindle in metakinesis.

Fic. 15. Longitudinal section through both polar globules, 3 to 4 hours older
than egg represented in Fig. 14.

Fic. 16. Surface view of the median dorsal portion of an odthecal egg about 10
hours old. fg? fg, polar globules; 9? fz, female pronucleus (out of focus).

Fic. 17. Median longitudinal section of dorsal portion of an oGthecal egg. a,
dorsal contour; @ fz, female pronucleus just after leaving the polar globules.

Fic. 18, Longitudinal section of circumnuclear region, from near the middle of
the homogeneous yolk, with female pronucleus. The arrow in this and the following
figures points in the direction of the cephalo-caudal axis of the egg.

Fic. 19. Longitudinal section of circumnuclear portion of egg, one-third the length
of the egg from the cephalic pole. a@, dorsal contour; 9 fz, female pronucleus;
& px, male pronucleus.

Fic. 20. Longitudinal section of circumnuclear area from middle of homogeneous
yolk. @ fx and P gx, male and female pronuclei conjugating.

Fic. 21. Longitudinal section of circumnuclear area from the middle of the front
portion of the homogeneous yolk. Cleavage nucleus.

Fic, 22, Cleavage nucleus preparing to divide. cf, cytoplasm.

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376 WHEELER.

DESCRIPTION OF PLATE XVI.
Blatta germanica.

Fic. 23. Cleavage nucleus dividing. a, points to the ventral contour. The nucleus
in this egg had moved out into the granular yolk some distance.

Fic. 24. Two nuclei; @, seen in lateral, and 4, in polar view, from an egg contain-
ing 4 nuclei in the metakinetic stage of division.

Fic. 25. Ventral third of a transverse section of an odthecal egg; @ and 4, cells
which have just reached the surface. The amceboid cell in the interior is on its way
to the surface.

Fic. 26. Corresponding section of the somewhat older egg (Fig. 36). @, a
group of cells formed by tangential akinesis from one of the nuclei, like @, Fig. 25.

Fic. 27. Ventral third of a transverse section of an egg in the blastoderm stage;
6 days old.

Fic. 28. Ventral third of a transverse section. Blastoderm contracting. At 2’,
yolk nucleus being given off; at «, one which has sunk deep into the yolk.

Fic. 29. Transverse section through e, of an embryo like the one represented in
Fig. 43. v, yolk-cell; sd, mesoderm; ecd, ectoderm.

Fic. 30. Transverse section through e! of the embryo 43. a@, amnion; 57, serosa;
ecd, ectoderm; msd, mesoderm; 7, yolk-cell.

Fic. 31. Transverse section through the point fc/ of Fig. 41. ecd, ectoderm; 7z,
yolk-cell; #zsd, mesoderm.

Fic. 32. Transverse section through a point a little in front of as of Fig. 43. am,
amnion; sv”, serosa; ecd, ectoderm; msd, mesoderm; 7v, yolk-cell. «

Fic. 33. Surface view of blastoderm, showing the binucleolate nuclei.

Fic. 34. Enlarged view of syncytium «, in Fig. 36; showing the unequal size of
the nuclei.

Fic. 35. @ and c, surface nuclei in akinetic division from an egg in the same stage
as Fig. 36; 4, serosa nucleus in akinesis from a much older egg.

Fic. 36. Surface view of an egg shortly after the nuclei have begun to appear
on its surface. c, cephalic end; s, sinus; v, ventral surface; dd, dorsal surface; x, a
group of nuclei like that seen in section at a, in Fig. 26.

Fic. 37. Surface view of an egg in the blastema stage; 4 days old.

Fic. 38. Long. sect. along the carina cz, of Fig. 41; through the depression 4.
sv, serosa; 4, depression; ecd, ectoderm; msd, mesoderm; 7, yolk-cells.

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378 WHEELER.

DESCRIPTION OF PLATE XVII.
Blatta germanica,

Fic. 39. Diagram of a median longitudinal section of an egg to show paths of
nuclei, Explanation in the text.

Fic. 40. Diagram of a transverse equatorial section of an egg to show paths of
nuclei. Explanation.in the text.

Fic. 41. Surface view of the ventral face of an egg 7} days old. cw, carina; fci,
beginnings of procephalic lobes; 4/, depression (blastopore?) in the middle of the
rounded area of proliferation.

Fic. 42. Surface view of the ventral face of an egg 8 days old. a@s, amnion and
serosa beginning; /c/, beginning of procephalic lobes.

Fic. 43. Surface view of an embryo in “slipper” stage. @s, amnion and serosa.

Fic. 44. Surface view of an embryo in the “ hammer” stage, 9} days old. 0, open-
ing in amnion and serosa over the oral region; a, antennary lobe; /, beginning of
the second thoracic appendage.

Fic. 45. Embryo about 11 days old, isolated from the yolk. /, labrum; s¢, stomo-
dum; cgi, brain; a¢, antennary lobe; md, mandible; mx}, mx, 1st and 2d maxille;
p' to 7%, thoracic appendages; as, amnion and serosa; ¢f/, caudal plate.

Fic. 46. Embryo just after rupture of amnion and serosa; about 14 days old. 4,
cephalic end of yolk; oc, eye; ad, fat body, ast, anal stylets; f4, appendages of Ist
abdominal segment; remaining references same as in Fig. 45.

Fic. 47. Front view of same embryo. References the same as in Fig. 45.

Fic. 48. Embryo almost ready to hatch. oc, eye; ¢g/, brain; g/*, infracesophageal
ganglion; g/® to g/®, the three thoracic ganglia; g/1, last of the abdominal ganglia;
oe, cesophagus; ¢, crop; gz, gizzard; Az, heart; s¢, stomach; vc¢, rectum; mpg, Mal-
pighian vessels; as/, anal stylets; y, yolk; 2, labrum; zd, mandibles; mx! and
mx, Ist and 2d maxille; /! to £3, thoracic appendages; a/, antenne.

Fic. 49. Blatta germanica about a day after hatching.

Fic. 50. Sagittal longitudinal section through the middle of the dorsal organ from
an embryo 16 days old. a, anterior; 4, posterior end of dorsal organ; 0, depression;
v, a yolk nucleus.

Fic. 51. Frontal section through the anterior end of dorsal organ in an embryo 18
days old. cc, heart; #7, nuclei of serosa cells; 0, cavity formed from the depression
o, of Fig. 50; v, yolk nucleus.

Fic. 52. Cross-section through the dorsum of an embryo to show formation of the
heart. 4, cavity of heart; cé cb, cardioblasts; ecd, ectoderm; sm, somatic mesoderm;
slm, splanchnic mesoderm; ex¢, entoderm; 4/, blood corpuscle becoming loosened
from the wall of the heart; , yolk.

Fic. 53. Cross-section through the thorax of an embryo 12 days old. #7, neural
thickening; a, amnion; sv, serosa; v, yolk nucleus; sd, mesoderm; c/, coelomic
cavity; #?, second pair of legs.

Fic. 54. Cross-section through 2d maxillz of an embryo 16 days old. x?, second
maxilla; g, duct of salivary gland; y, yolk; ev¢, entoderm; cé, cardioblast cells;
remainder of references as in Fig. 53.

Fic. 55. Cross-section through the basal abdominal somite of an embryo 26 days
old. gi, ganglion; ad, corpus adiposum; 7, yolk nucleus; 7/7, tracheal opening; 4,
yolk; cc, heart.

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380 WHEELER.

DESCRIPTION OF PLATE XVIII.
Doryphora decemlineata.

Fic. 56. Portion of a longitudinal section through a young egg shortly after the
germinal vesicle has reached the periphery. //, karyoplasm; ¢, protoplasmic trabe-
culz connecting the karyoplasm with the intervitelline protoplasm (cytoplasm of the
large cell which the egg represents); y, yolk bodies; ¢f, follicular epithelium; 74
germinal spot (nucleolus); 74, maturation balls (Reifungsballen of Stuhlmann) Zeiss
zz, oc. ITI.

Fic. 57. Section corresponding to that of Fig. 56 from an egg almost mature.
n, large mass of chromatin destined to enter into the first polar spindle; 4/, layer of
surface protoplasm; y, yolk bodies; ef, follicular epithelium. Zeiss 7'z, oc. III.

Fic. 58. Longitudinal section of a mature egg. , resting nucleus originating from
the mass of nuclein 2 of Fig. 57; 4/, differentiated peripheral layer of protoplasm;
yy yolk bodies; z, vitelline membrane; ch, chorion. Zeiss 7/5, oc. ILI.

Fic. 59. Portion of median transverse section of a mature egg. 7, first polar spindle
in metakinetic stage; remaining references the same as in Fig. 58. Zeiss 3/5, oc. III.

Fic. 60. Same section as in Fig. 59 of an cgg about to be deposited, nucleus
in last stages of anaphasis; the peripheral mass /! the first polar globule. Remaining
references the same as in Fig. 58. Zeiss ;',, oc. III.

Fic. 61. Half of the median transverse section of an egg containing several nuclei
1, n3, none of which have as yet entered the surface layer of protoplasm é/. y, yolk.

Fic. 62. Half of the median transverse section of an egg shortly before the blasto-
derm stage. v, yolk-cells; a, blastema cell resting; 4, blastema cells in metakinesis;
c, blastema cells in anaphasis; 4, yolk.

Fic. 63. Half of the median transverse section of an egg in the blastoderm stage.
v, yolk-cells; d/d, blastoderm.

Fic. 64. Half of a median transverse section of the egg of Fig. 67. g, half of the
gastrular groove forming on the ventral face; 7, ridge separating the groove-from the
remainder of the blastoderm; J, flat blastoderm cells on the dorsal surface of the egg.

Fic. 65. Median transverse section of an egg carrying the embryo represented in
Fig. 71. The upper half of the section passes through #? of Fig. 71, the lower half a
little in front of x. sv, serosa; am, amnion; ecd, ectoderm; msd, mesoderm; e77,
cells still forming part of the induplicated ectoderm at f/. which give rise to the ento-
derm; y, yolk.

Fic. 66. Ventral view of egg shortly after formation of blastoderm; the two paren-
thesis-shaped ridges inclose the portion which will sink in to form the gastrula.

Fic. 67. Ventral view of egg with gastrula more advanced. a, oral spade-shaped
broadening of the gastrula; 4, the point at which the groove turns abruptly inwards;
sv, serosa.

Fic. 68. Lateral view of same egg. c/, procephalic lobes; remaining references
the same as in Fig. 67.

Fic. 69. Caudal end of egg represented in Fig. 70. g, gastrula; a, caudal fold
of the amnion; 5s”, serosa.

Fic. 70. Ventral view of an egg with gastrula fully formed. a, oral widening of
the gastrula; am, cephalic fold of amnion; 47, brain thickening.

Fic. 71. Slipper-shaped embryo removed from egg and unrolled. 1 to f%, indica-
tions of the 3 pairs of thoracic appendages; as, amnion and serosa; am, cephalic
fold of amnion and serosa; @, oral and x, anal end of gastrula; 4, maxillary region.

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382 WHEELER.

DESCRIPTION OF PLATE XIX.
Doryphora decemlineata.

Fic. 72. Embryo shortly after the appearance of the appendages, unrolled and iso-
lated. 0, stomodeum; a, proctodeum; /, labrum; 4! to 63, three brain segments;
og! to og, three segments of the optic ganglion; of! to of%, three segments of the
optic plate; @ to 2°, five pairs of invaginations which form the tentorium; 7 to 7,
tracheal invaginations; the two last pairs 7° and 2, either disappear or form the
openings of the sexual ducts; @/, antenne; md, mandibles; mx) and mx, first and
second maxilla; /! to £%, three pairs of thoracic appendages; ¢c, commissure con-
necting the two ganglionic thickenings g* of the intercalary segment; g/, ganglionic
thickening; mzs/, Mittelstrang thickening; mfg! to mpg*, three Malpighian vessels.

Fic. 73. Embryo just after the closing of the amnion and serosa (s7) unrolled and
isolated. a, oral, x, anal end of the gastrula; fc/, procephalic lobe; m.«?, second
maxilla; #1 to #, three thoracic appendages; cf, caudal plate.

Fic. 74. Ventral view of embryo, the lateral walls of which have embraced half
the yolk; references same as in Fig. 72.

Fic. 75. Lateral view of embryo ready to hatch. a, antenna; ¢%, mesothoracic
spiracle; 7! to ¢18, abdominal spiracles; /sf, first hatching-spine.

Fic. 76. Sagittal section to one side of the median line through the tail of embryo,
Fig. 72. am, amnion; s7, serosa; mpg! and mpg%, first and third Malpighian
vessels; ecd, ectoderm; msd, mesoderm; ev¢, forward growing band of entoderm;
ent', mass of entoderm left under the end of the proctodzeum.

Fic. 77. Transverse section through the second pair of Malpighian vessels (mg)
of the same embryo. x, proctodzeum; other references same as in Fig. 76,

Fic. 78. Median cross-section through an egg containing an embryo a little older
than that represented in Fig. 72. The section cuts the embryo at two places. That
with the entoderm (e/) belongs to one of the last abdominal segments, that withou*
entoderm to one of the basal abdominal segments. 27, neural thickenings; ecd and
ent, ectoderm and entoderm; s/m, sm, splanchnic and somatic mesoderm, inclosing
the coelomic cavity; cd, cb, cardioblast cells.

Fic. 79. Cross-section through the middle of the proctodzeum of an embryo some-
what younger than that represented in Fig. 74. x, proctodzeal cavity; c/, coelomic
cavity; g/, ganglion; mst, Mittelstrang; mpg! to mpg’, Malpighian vessels sur-
rounded by mesodermic elements.

Fie. 80. Cross-sections through the sexual orifices of an embryo in the stage of
Fig. 74. go, go, openings of efferent ducts; remaining references as in preceding
figures.

Fic. 81. Surface view of two eyes (corresponding to eyes V. and VL. of Aczdéus as
described by Patten). 7, large nucleus in the centre of each eye.

Fic. 82. Median sagittal section through an embryo in about the stage represented
in Fig. 73. @m and sv, amnion and serosa; 0, point at which the anterior end of
the embryo passes into the amnion; /, point at which the posterior end passes into
the amnion; sf, stomodzeal depression; x, point near which the proctodzum will
appear; #/1, f/*, anterior and posterior thickenings of the inner layer; from which
the entoderm, ent}, ent?, originate. msd, mesoderm; mx! and mx, first and second
maxille; 4! to £3, legs; c, cells which entered the amniotic cavity. Under the two
thickenings 7/1, f/?, are seen the peculiar degenerating nuclei passing into the yolk,
which has become segmented.

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384 WHEELER.

DESCRIPTION OF PLATE XxX.
Doryphora decemlineata.

Fic. 83. Portion of cross-section through a basal abdominal segment of an em-
bryo somewhat younger than that represented in Fig. 74. @7, amnion; ev/, entoderm;
ect, ectoderm; ¢, tracheal invagination; g/, ganglion; ms¢, Mittelstrang; sv, somatic
mesoderm; s/z, splanchnic mesoderm; cé, cardioblasts.

Fic. 84. Transverse section through middle of abdomen of embryo, Fig. 74. gn,
sexual organ; mg, Malpighian vessel; remaining references same as in Fig. 83.

Fic. 85. Cross-section through metathoracic segment of an embryo considerably
older than Fig. 74. /z, lateral nerve trunk; af, appendage; sv, serosa; ad, fat cells;
a, amnion cells entering the yolk at 4; remaining letters the same as in Fig. 83.

Fic. 86. Cross-section through mesothorax of an embryo after the formation of
the heart, 4¢. Asp, thickening of ectoderm which secretes the metathoracic hatching-
spine; c/\, first cuticle shed by the embryo; cm, longitudinal commissures between
two thoracic ganglia; f, furca; 7, point of attachment of muscles to the furca; ms/,
muscular tissue; remaining letters as in preceding figures.

Fic. 87. Cross-section through caudal plate of embryo before the closure of the
anal end of the gastrula, w. <¢, cell about to wander through the blastopore into the
amniotic cavity; sd, mass of cells which will form the mesoderm as soon as the blas-
topore closes; evz/, cells imperfectly differentiated from those of the mass, 7zsd, which
are to give rise to the entoderm; vz, yolk nucleus; @, amnion; 57, serosa.

Fic. 88. Cross-section, more highly magnified than the preceding, through the
caudal plate of an embryo somewhat younger than that of Fig. 73. The blastopore
has closed, and the depression « marks the beginning of the proctodzal invagina-
tion; Z is the line, unusually distinct in the section figured, separating the mass of
mesoderm cells (msd@) above it from the smaller mass of entoderm cells (ev?) below
it; ¢ 0, v, degenerating nuclei which pass from the entoderm into the yolk; y, yolk
nucleus.

Fic. 89. Frontal section through the cardioblasts (cd) of an embryo in the same
stage as Fig. 84; cb, row of cardioblasts; ecd, msd, ent, germ layers; ad, fat cells.

Fic. 90. Portion of a cross-section through the lower part of the dorsal yolk of
an embryo in the stage of Fig. 74. ch, chorion; sv, serosa; am, amnion; do, amniotic
dorsal organ; m, amniotic nuclei degenerating; v, yolk nucleus.

Fic. 91. Frontal section through the meso- and meta-thoracic ganglia of the em-
bryo, Fig. 74. cm, longitudinal commissures; ccm, cross-commissures ; n\, anterior
nerve trunk; #2, posterior nerve trunk; ov7/, outer neurilemma; znr/, inner neu-
rilemma.

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DESCRIPTION OF PLATE XXI.

Doryphora decemlineata.

Fic. 92. Sagittal section through stomodzum (sf) of an embryo in the same stage
as Fig. 72. ecd, ent, msd, germ layers; /0, labrum.

Fic. 93. Cross-section of median dorsal portion of an embryo, just after the union
of the ectoderm (ecd) from either side of the body; cé, cardioblasts; ad, fat cells;
am, one of the last amnion cells passing into the yolk through the opening between
the two lateral halves of the mesenteron. zs/, muscular tissue; e7/¢, entoderm; s/m,
splanchnic mesoderm.

Fics. 94 to 104. Sections 1, 3 to 8, 10, 11, 13, and 14, through the mesothoracic
ganglion of an embryo somewhat younger than that of Fig. 74. cw, longitudinal
commissure; ccm, cross-commissures; #s, Punktsubstanz; mzs¢, Mittelstrang; ecd and
e, hypodermis; g4/, ganglioblasts.

Fic. 105. Section through fore part of metathoracic ganglion. The Mittelstrang,
ist, persists as the fzca (subsequently chitinous). g/, ganglion; fs, Punktsubstanz;
visi, muscular tissue attached to the furca; ecd, hypodermis.

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Volume II, December, 1889. Number 3,

JOURNAL

OF

MORPHOLOGY.

THE EMBRYOLOGY OF THE EARTHWORM.

EDMUND B. WILSON.

CONTENTS.
PaRT I. oak
Te LOGUCHON 4c cis cic otlalsiae clniters's ctv wate cece cccceue feline eietaielays 388
Part II.

TY. Ege-laying, Ct. ois 0.s'ses cisec's cais's nlnimls mii sle'e sin wicieiaise sisicinis's s Seow, lel!
III. Cleavage of the ovum and origin of the layers ........+.2.seeeseeeee 396
MiVare Gastrulation is.) <cre -s-retate'sts)Notataohelateve) si vansletaletay shelelsialelevalelel ein aietele loci sedate 399

V. General history of the germ-bands ........sseeee cece ere eee rene eees 401

Kee Dive) Mes blast. ccc sineintere) sisieiereie ater cle a) stoeiverdlaveletakere(olarteie(aislalele 401

Dor HevectOblast: .«:cfterajelvieha/otereyetalevsteyolereteratstolet-ekalelel=iaia iat s{-/=tskeliate 401

3. Larval execretory Organs ......... eee e eee e eee c eee eeeeeeeees 401

4. Middle stratum 2... 2... ccc sceeccec cern nccenscseencscccee 402

5. The teloblasts .........sceeee seer erer cece eneteeeescenaees 403

VI. General history of the mesoblast .......ccceesessececcccceseveceoes 404.
Be General: CierentiallOn. ale cc salets|se fers /elessialelcieletels sieisiely o}<istelstete 404

pee (Goel om Cacavittese siaicterieictersiois stale atsieisiatelel che) steleletefetersie eiatet sede 406

3. Vascular system ....ccesccee recs ces cvccecsesecnesesancce 408

WAIL, Tit DIESTAMEE Sere OO te De bOo SO GOOUIGIe TOOc Moon oOGs GO Gaco HuGn AmcAS 410
VIII. The Ectoblast and its products... ...cececcseccnccencscccsescessess 4II
iy Ganaril 4566 socoocounneacdocacpanopocsorococnesesaounT 411

PHS TOM OMS [MI steleteieieieleletere) cf eiel aie csteietahelleleverel eforalimjetaietoreliausvujaelsevatete 412

3. Proctodaeum.....cecessseeeccececssccesecncecssccecencece 414

TEGs Nervous GyStent « jaiainie s:ojei5:2:0 cl ojein aie ofall faraje aimyufe ale ole = nualmieimie Ams pla\sia uote 415
1. Relations of the cephalic ganglia to the ventral chain.......... 416

2. Concrescence of the neural cords. ........eeeeeeseeccssseses 417
MecBxeeretory Organs ..0.5. cen ecccs seccwemeeseneresassscideeces ates 419
Tas UNtLOCUCEOKY \c}a/s)ccje)scjalete elesieis ss v= sls) 'einic sago Noue osadccdnde 419

2. Head-kidney ........ sicoococadsdenoc Jats sonacneaGa7d6ac 422

3. Permanent nephrida.......... LEA OSOHOE SohodennacnooGennse 423

388 WILSON. [Vou. If.

ParT III.
PAGE
XI. Relations of the head [prostomium] and trunk ..............0ec00ee 429
I Concrescence and thes blastopore) s-yiesie spieminienn setae ioe ete See eierieiele 435
SCM Lheitrochosphere and thesteloblasts meer micii-inc lest cieieeletaleeeeietere 439
UV er Mesoblast and coclommcceretayehelayareraieleletsielclehetate sistaletaraimicicieie ateretoieieietneieiots 442

PART I.— INTRODUCTORY.

I. Tue following paper contains the results of an examina-
tion of the development of the earthworm that has occupied
my attention at intervals for a considerable time. I shall not
attempt to give an exhaustive account of the development, and
I must leave unsolved a number of important problems, some
of which can perhaps only be fully elucidated by the study of
other and more favorable material. The results already attained
differ widely, however, from generally accepted views in respect
to many important phenomena and clearly show the need for a
re-examination of many features of annelid development, even
in the case of forms that have already been carefully studied.

It is hardly necessary to call attention to the historical im-
portance of Kowalevsky’s pioneer researches on the embryology
of Lumbricus and Euaxes (No. 27), or to the interest of the
questions suggested by Kleinenberg’s later and more detailed
studies (No. 28). Both these works have played an important
part in the advance of comparative embryology, and must
always command the admiration of morphologists. Both were
nevertheless far from exhaustive ; and later investigations have
left our knowledge of the subject not only incomplete, but as
I shall endeavor to show in the sequel, obscured by a false
conception of some of the most important phenomena of de-
velopment.

The more important results of my work may be briefly sum-
marized as follows :—

(1) The cleavage is unequal and variable, and results in
the formation of a blastula containing a large blastoccel. The
gastrula is formed by embolic invagination. The blastopore,
which at first occupies the entire ventral surface, narrows toa
slit-like form, its longer axis coinciding with the long axis of the
adult body; it then closes from behind forwards, its foremost
portion persisting as the mouth. The germ-bands are already
established at the time of the invagination and lie at the sides

No. 3.] ZHE EMBRYOLOGY OF THE EARTHWORM. 389

of the primitive blastopore. They are from the outset united
in the middle line behind the posterior lip of the blastopore,
but remain separate in front until the establishment of the
mouth, when they extend forward, join in the median dorsal line,
and thus form a complete longitudinal ring surrounding the
region of the primitive blastopore.

(2) The entire mesoblast is derived from a pair of primary
mesoblasts or teloblasts that lie at the posterior ends of the
germ-bands, and no mesoblastic elements arise from the ecto-
blast overlying the germ-bands. The primary mesoblasts are
differentiated in the course of the cleavage and are pushed into
the segmentation-cavity some time before the beginning of
gastrulation, in the manner described by Kleinenberg (No. 28).
The cells formed by the continued proliferation of these primary
mesoblasts are at a very early period differentiated into two
groups which, though having a common origin and remaining
in continuity, may conveniently be designated by different
terms.

The cells of the first group have histologically the character
of mesothelium, form the mesoblastic parts of the germ-bands in
the trunk region, and enclose the paired ccelomic cavities. They
may therefore be called collectively the ¢runk-mesoblast. The
cells of the second group arise by migration from the dorsal and
anterior parts of the germ-bands, and may therefore be called
the migratory mesoblast. They have histologically the character
of mesenchyme, and form a nearly complete investment of the
body in the trunk region, but also extend forward to form the
cephalic mesoblast of the praoral lobe or prostomium. [It
should be clearly understood that this distinction is made solely
for the sake of convenient description, and that all the cells of
both groups arise from the two primary mesoblasts and from no
other source. ]

(3) When fully established the germ-bands consist of three
strata of cells, as in Hirudinea, namely: (2) an outer stratum
(ectoblast), one cell in thickness, which arises directly from the
original outer layer of the gastrula, and persists as the hypoder-
mis; (4) an inner stratum (mesoblast) consisting of granular
cells derived from the two primary mesoblasts; from it arise
the muscles, dissepiments, blood-vessels, peritoneal epithelium,
reproductive organs, and the inner part of the nephridia; (¢) a

390 WILSON. [Vor. III.

middle stratum which lies between (a) and (4) and agrees in
general histological character with the ectoblast (from which
it is indirectly derived). From the middle stratum arise (a) the
nervous system, (4) the outer part of the nephridia, (¢) the
setigerous glands and the sete.

(4) The middle stratum is arranged in a series of distinct
longitudinal cell-rows which, in early stages, lie at the surface
and form part of the general ectoblast, but afterwards sink
below the surface and are completely covered by the remaining
ectoblast. Of these rows there are either three or four in each
germ-band. The inner (or ventral) row gives rise to the cor-
responding half of the nervous system, and will therefore be
called the xeural row, or cord. The two succeeding rows on
each side give rise to a portion of the nephridia and to the
inner series of setigerous glands, and will be called the xephric
vows. The fourth or outer row, which I have found as a dis-
tinct structure in one species only, gives rise to cells which
form the outer or dorsal part of the middle stratum. Their
precise fate is still in some doubt, but it is probable that they
give rise to the outer series of setigerous glands, though perhaps
to other structures as well.

(5) Until a comparatively late stage each row of the middle
stratum terminates behind in a large cell (teloblast), which is
the parent of the entire row, and thus of all the structures to
which the row gives rise. The inner teloblast will therefore
be called the zeuvoblast, those at the ends of the nephric rows
the zephroblasts; the fourth, owing to the uncertainty of its
fate, will be called the /ateral or outer teloblast. These four
teloblasts may be called the anterior teloblasts to distinguish them
from the posterior or mesoblastic teloblasts which lie at the
extreme hinder ends of the germ-bands.

(6) The teloblasts of the middle stratum are at first ordinary
ectoblast cells which cannot be distinguished from the adjoining
cells. They first appear shortly after the completion of gas-
trulation, and at this time lie at the surface, like the rows (now
very short) to which they give rise. At a later period they
sink below the surface and ultimately break up into groups of
cells lying at the hinder ends of the corresponding rows.

(7) The cephalic lobe (prostomium) arises by the union of
the anterior ends of the germ-bands. The mesoblastic part

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 391

arises by the forward growth and union in the median line of
the mesoblastic bands, a process which is effected by prolifer-
ation and migration of the mesoblast cells already formed, and
not by the formation of new mesoblastic elements from the
superjacent ectoblast. The prostomial cavity is from the very
first unpaired.

(8) The przoral or cephalic ganglia are differentiated out of
the front ends of the neural rows at a time when these rows are
fused with the ectoblast, and before they have met in the
median line in front of the mouth. There is therefore no
median apical plate (Scheitelplatte), but only a pair of lateral
ectoblastic thickenings continuous behind with the neural rows.
I am unable to say positively whether the cephalic ganglia actu-
ally arise from the neuroblasts, but I believe they do not [p. 416].

For more special accounts of the origin and differentiation of
the layers and the detailed development of organs, the reader is
referred to Part II. It is, however, desirable to preface the
special descriptions with a short discussion of their relation to
the work of other investigators.

The principal questions suggested by my work relate to the
origin of the mesoblast and the history of the middle stratum of
the germ-bands. The existence of this stratum in the germ-
bands of Oligochzeta has not hitherto been distinctly recognized,
though Kowalevsky and Kleinenberg indicate it in their figures
of Lumbricus. The nephric and outer cell-rows and the four
anterior teloblasts have hitherto been observed only in the
Hirudinea and adequately studied only in the single case of Clep-
sine. As regards the mesoblast, I am fully convinced that the
whole of the “epiblastic mesoblast”” which Kleinenberg believed
to be derived directly from the outer layer, is simply the middle
stratum which he failed to distinguish from the inner or meso-
blastic stratum. This misinterpretation has importance because
of the emphasis which Balfour placed upon Kleinenberg’s con-
clusions, and still more on account of its connection with the
views put forward in Kleinenberg’s recent remarkable paper on
Lopadorhynchus (No. 31). In this masterly work the author not
only rejects the ordinary conception of the mesoblast, but even
goes so far as to deny its existence as a primary feature of devel-
opment, all “mesoblastic”’ structures being conceived as direct
or indirect derivatives of the two primary layers, ectoblast or

392 WILSON. [VoL. III.

entoblast, which alone are of fundamental significance. With-
out presuming to question the justness of these conclusions,
which are certain to exercise an important influence on embry-
ology, I wish to point out the fact that Kleinenberg’s views
appear to have been influenced in a measure by his conclusions
in respect to the origin of the “mesoblast” in Lumbricus, and
that these conclusions are certainly erroneous. In his paper on
the development of the earthworm Kleinenberg obviously means
that the layer of cells ordinarily called “mesoblast” in this
animal —that is, the layer of undifferentiated cells from which
the muscles, blood-vessels, dissepiments, peritoneal epithelium,
and reproductive elements arise —has a double origin, part
arising from the primary mesoblasts at the posterior ends of
the germ-bands, but a greater part being directly derived by
proliferation of the overlying ectoblast. But after the most
careful study of the question by means of complete series of
sections of all stages of development, I can assert positively that
this is not the case. It is true that new elements are added to
the germ-bands from the ectoblast; it is not true that these
elements assume the character of mesoblastic cells and give
rise to structures ordinarily recognized as mesoblastic. On the ©
contrary, they are from first to last ectoblastic structures in the
sense of being derived from the outer layer of the gastrula long
after the layers are completely established, in retaining the
histological characteristics of the ectoblast, in remaining long
embedded in that layer, and in giving rise to structures (nervous
system, setigerous glands ) that in other forms are unquestionably
of ectoblastic origin ; and it would lead to hopeless confusion in
the use of terms to regard the middle stratum as forming a part
of the “ mesoblast,” taking the word in the sense employed by
Kleinenberg in his paper on Lumbricus. It is furthermore
perfectly clear that the middle stratum of Lwméricus in no way
represents that part of the “ mesoblast’”’ (using the word in the
ordinary sense) that is split off from the ectoblast in Lopadorhyn-
chus (e.g. the muscle-plates ), for there can be no question that
the muscles, dissepiments, vessels, peritoneal epithelium, repro-
ductive organs, and a part of the nephridia, are derived from the
inner or mesoblastic stratum, and hence ultimately from the two
primary mesoblasts.

This preliminary explanation will, I trust, make plain in what

No. 3.] ZHE EMBRYOLOGY OF THE EARTHWORM. 393

respect, apart from all differences of terminology, my views
differ from those of Kleinenberg, and will prevent confusion in
the use of terms. I may add lastly that some of my conclusions,
especially those relating to the origin of the nephridia, have
been criticised by a number of writers, notably by Bergh (No. 8),
whose remarks are, however, couched in such terms as to render
a reply unnecessary. A careful re-examination of the whole
subject has not essentially altered my original view, though I
am ready to admit having perhaps been somewhat too positive
in my statements as to the origin of the nephridia. I trust
that the present paper will at least present clearly the evidence
on which my conclusions were based.

PART II.— DESCRIPTIVE.

I have examined the development of three species to which I
shall refer respectively as Lumbricus terrestris, L. communis, and
L. fetidus, though the latter two forms are placed by most
recent writers in the genus A//olobophora, and the specific name
communis has been discarded.!

The three species agree closely in the general outlines of
their development, as far as I have been able to follow them,

1Vejdovsky [No. 44] gives the following names to these species; I add also a
partial synonymy, as given by the same author, which will suffice to identify the
forms I have studied.

1. Lumbricus terrestris L., = L. agricola Hoffmeister.

2. Allolobophora cyanea, = Enterion cyaneum Sav., = Lumbricus communis cyaneus
Hofim., = Allolobophora turgida Eisen.

3. Allolobophora fetida Eisen = Enterion fetidum Sav., = Lumbricus fetidus Dugés,
= L. olidus Hoffm.

According to Vejdovsky the form studied by Kleinenberg has the following

synonymy : —
Allolobophora carnea, = Enterion carneum Sav.,= Lumbricus trapezoides Dug.,
= L. communis carneus Hoftm., = Allolobophora mucosa Eisen.

Ude, however, accepts Eisen’s names for the two species included under Hoff-
meister’s “ Z. communis,’ and in view of this disagreement I have preferred to use
the specific name communis. I prefer to apply the generic term Lumédricus to the
three species I have studied, partly for the sake of brevity, but more especially because
Eisen’s division of the earlier genus Lzmébricus into Allolobophora and “ Lumbricus”
is based upon a trifling anatomical distinction which does not correspond to the
differences I have observed in the mode of development — z.e., the two species of
“ Allolobophora” (L. communis and L. fetidus) differ somewhat in development, and
one of them agrees precisely with Z. cerrestris, which is a typical “ Lumbricus” in
Eisen’s sense,

394 WILSON. [Vor. III.
though they differ in some interesting details. I have relied
mainly upon L. fetidus for the early stages, but L. communts
and L. terrestris are much better adapted for the later develop-
ment, since in L. fetidus the albumen becomes so hard as to
render section cutting well-nigh impossible without removal
of the contents of the archenteron. I have also examined .
embryos of a species of small fresh-water Oligocheete (see Figs.
55, 50) which I have been unable to identify with the adult form.

EI. -EGG-LAVING; ETC:

In spite of many individual variations, the egg-capsules of
the various species of Lambricus are, as a rule, readily distin-
guishable in form, color, and size. Those of L. fetidus, which
are laid in and about manure-heaps, are rather regularly fusi-
form, varying in color from light yellowish to dark brownish
olive; they measure on the average about 4-6 by 2-3 milli-
meters. The albumen is tough and jelly-like, dissolves with
difficulty in water, and becomes of a horn-like consistency after
the hardening action of reagents. Each capsule contains from
ten to sixty ova, of which not more than ten or twelve undergo
development, and this number may be reduced to one or two,
particularly in the winter season. The capsules of L. communis
and L. terrestris are deposited in earth, usually a few inches
below the surface. Those of the first species are irregularly
fusiform, and of a brighter yellow color than those of L. fetidus ;
they measure on the average about 5-7 by 3-5 millimeters.
Those of ZL. terrestris are still larger (mean measurements
are 6-8 by 4-6 mm.), regularly fusiform, but more swollen and
rounded than those of the other species; their color is a dark
olive. In both species the albumen has a slimy, mucus-like
consistency, and is not greatly hardened by reagents. In Z.
terrestris only one egg develops out of several included in the
capsule. In ZL. communis two embryos are produced as a rule,
and in many cases, though not in all, both arise as twins from a
single ovum, as has been described by Kleinenberg.

Egg-laying seems in special cases to continue throughout the
year, though it is most active in the spring and summer months.
I have found the capsules of ZL. fetédus out-of-doors in nearly
every month of the year, but in mid-winter they are only found

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 395

in decomposing compost-heaps where the temperature is main-
tained at a tolerably high point. The rate of development
varies greatly, and depends not only upon the temperature, but
also upon the vigor or other internal properties of the individual
embryos, for in late stages the embryos in a single capsule are
often found in very different stages of advancement. It is
therefore impossible to determine the age of the embryo with-
out following its actual development. In laboratory cultures
the young worms usually make their escape from the capsule in
about two or three weeks.

For the present I am obliged to pass over the phenomena
relating to the maturation and fecundation of the ova, and my
account of the cleavage will be found unsatisfactory, owing to
the impossibility of following continuously the development of
the individual ova. Development continues for some time
after removal of the segmenting ova from the capsule, but
pathological changes invariably supervene, however careful the
treatment, and I am persuaded that no trustworthy results can
be obtained by this method. After making numerous drawings
of embryos thus studied, I rejected them all, and relied wholly
on the comparative study of specimens examined or preserved
immediately after opening the capsules. The results thus
obtained, though based on the examination of a very large
number of specimens, are necessarily incomplete; but I believe
them to be trustworthy as far as they go.

As in so many other cases, periods of quiescence, or “ resting
stages,” alternate with periods of division throughout the cleav-
age process. In the resting periods the cells are closely pressed
together, and their outlines are often hard to see; so that it is
weil-nigh impossible to interpret some of the stages unless they
are studied in the active period. Moreover, the cleavage process
varies greatly in the order of division, which after the first two
divisions loses all appearance of regularity. On account of these
circumstances the segmenting ova vary widely in appearance,
and the process of cleavage thus acquires that apparent irreg-
ularity which other observers have found so perplexing. It is
now well known, however, that the segmenting ova of various
other animals (e.g. Mollusca, Coelenterata) are likewise subject
to considerable variation, which in some cases at any rate is due
simply to temporary acceleration or retardation in the divisions

306 WILSON. (VoL. III.

of individual cells (No. 53), and probably does not affect the
essential character or the end-result of the cleavage. The
following description applies to L. fetzdus.

III. CLEAVAGE.

1. The fertile ova are slightly ovoid in shape and measure
about 0.125 mm. by 0.112 mm. They are surrounded by a
delicate vitelline membrane which is at first closely applied to
the vitellus, but afterwards enlarges so as to become widely sepa-
rated from it. The vitellus is laden with small, clear yolk-spheres
and granules, which only partially obscure its transparency and
usually do not prevent a clear view of the interior of the
embryo after suitable treatment with reagents. Several polar
cells are formed, probably by the division of two primary polar
cells directly separated from the ovum. They usually occur in
two groups of three or four each (Figs. 1 and 2) which lie in
the plane of the first cleavage, but appear afterwards to shift
their position so that no constant relation between them and
the embryo can be recognized. At the first cleavage the
vitellus divides into two unequal parts, the plane of division
passing through the polar cells (Fig. 2). The second cleavage
divides the smaller cell into two nearly equal parts, and (as I
believe) separates a third small cell from the larger of the first
two (Figs. 3-5). No constant difference in the granulation
of these four cells can be made out. In the ensuing resting
stage a distinct cavity appears between the’ three smaller and
the one larger cell, but this cavity disappears afterwards, and
cannot be identified with the true blastoccel. I have occasionally
seen apparently normal ova in which the four cells of this stage
are nearly equal in size, and others in which only three cells
were present. With the third cleavage normal variation cer-
tainly begins. Asa rule, the largest of the four cells shown in
Figs. 3-5 divides into. two equal parts, and the three smaller
cells lie in a group above the angle between them (Fig. 6). In
some cases, however, only two small cells are present. In the
next stage, as a rule, the number of small cells is increased
to four (Fig. 7), probably by division of one of the smaller
cells of the preceding stage, after which-each of the large cells
divides into two unequal parts (Figs. 8-14), the smaller of

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 397

which (3, 4) is intermediate in size between the four (or three)
small (5, 6, 7) and the two (1, 2) largest cells. In some cases,
however, the large cells undergo this division when only three
small cells are present, as shown in Fig. 10. At the end of this
period, therefore, the embryo consists of seven (Fig. 10), or eight
(Figs. 12, 13), cells, namely: two large equal cells (1, 2, Figs.
10, 11), two middle-sized equal cells (3, 4), and three or four
small cells (5, 6, 7, 8). The latter are probably situated at the
upper or ectoblastic pole.

From this time forward the divisions cannot be followed in
detail, but I do not believe that any definite order exists. When
the embryo consists of not more than twelve or sixteen cells a
large segmentation cavity appears, and the embryo becomes a
blastula, the walls of which consist of a single layer of cells
(Figs. 19, 20). At one pole these cells are smaller than at the
other, but it is not possible to draw any definite line between
micromeres and macromeres. The structure of the embryo at
this period may be understood by a study of Figs. 15-10,
which are accurate drawings of a single individual in several
different positions, so that every cell may be seen. There are
in all thirteen cells, which do not perceptibly differ in the char-
acter of the protoplasm, and I am unable to say what is the pre-
cise relation of these cells to those of earlier and later stages ;
or to recognize the future primary mesoblasts, though it is
possible that they are already present.

Comparative. — From the foregoing account it will be seen
not only that I have had no better success than Kleinenberg in
following the details of the cleavage process, but that my results,
as far as they go, do not fully coincide with his; and I can only
reconcile the discrepancy by supposing that, aside from indi-
vidual variation, there are some constant differences between
L. fetidus and L. “ trapezoides.”’ The two-celled and four-celled
stages appear to be essentially the same in these species; and
the same is true of the three-celled stage, though it seems to
occur more rarely in ZL. fetidus. Kleinenberg’s six-celled stage
corresponds closely with that shown in Fig. 7, but it would
seem, from his description, to arise in a quite different manner.
From this point to the full establishment of the blastula I am
unable to correlate Kleinenberg’s observations with my own.

A comparison of my figures with those of Whitman on C/ep-

398 WILSON. [Vot. III.

sine (No. 50), and Vejdovsky on Rhynchelmis (Nos. 45, 48),
shows that it is impossible to establish any certain homology
between these forms and Lumbricus. At first sight the four-
celled stage shown in Fig. 3 might seem to correspond with that
of Rhynchelmis, but the subsequent development fails to estab-
lish the comparison. The eight-celled stage (consisting of four
macromeres and four micromeres), which may be taken as char-
acteristic of the typical unequal cleavage, seems to have been
entirely masked by secondary changes in the cleavage periods,
and the facts are still too incompletely known to justify any
speculation as to the history of these changes.

The one positive result that seems to be brought out by the
comparison is that the phenomena of cleavage in Luwméricus are
of a highly modified character, and this conclusion is also indi-
cated by the individual variability of the segmenting ova. This
conclusion, unsatisfactory as it is, may have an important bear-
ing on the general interpretation of the process of gastrulation.

2. Origin of the Layers.— My observations on the origin of
the primary mesoblasts agree closely with those of Kleinenberg,
and show beyond all question that the mesoblast is differentiated
long before the invagination of the gastrula.

The changes resulting in the formation of the blastula usually
occupy from 18 to 24 hours. During the following 24 hours
(more or less) the cells increase rapidly in number by radial
divisions, the blastula remaining one-layered and nearly spher-
ical. Two of the larger cells lying side by side near the equator
of the blastula (Fig. 23) undergo no radial division, and their
inner ends soon project into the blastoccel. The inner ends
are then separated from the peripheral parts by tangential
divisions, which take place nearly at the same time in the two
cells. The two smaller cells thus formed lie side by side in the
blastoccel, which they nearly or quite fill (Fig. 25). The two
larger cells, which still lie at the surface of the blastula, are the
“primary mesoblasts,” which by continued divisions give rise
to the entire mesoblast. I have failed to trace the origin of
these cells in the process of cleavage, the original character of
which has been so altered that it is impossible to determine
the relation of the primary mesoblasts to the micromeres and
macromeres of the typical unequal cleavage. Fortunately, how-
ever, Vejdovsky has succeeded in following their mode of origin

No. 3.] ZHE EMBRYOLOGY OF THE EARTHWORM. 399

in Rhynchelmis, where they arise in a manner closely similar
to that studied by Whitman in Clepszne (Nos. 45, 48).

After the formation of the first pair of secondary mesoblastic
cells others are formed by successive divisions of the primary
mesoblasts, which in the meantime gradually sink below the
surface of the blastula and are finally quite included in the
cleavage cavity (Figs. 24-30). Thus arise two parallel rows
of mesoblastic cells which lie in the cavity of the still spherical
blastula and define the antero-posterior axis of the embryo.
Posteriorly the two rows terminate in the primary mesoblasts ;
anteriorly they join one another in the middle line. The
blastula retains its spherical form until five or six pair of second--.
ary mesoblastic cells have become formed and the primary
mesoblasts have become entirely enclosed.

This period is marked by the appearance of a large pore
(“cleavage-pore’’) opening from the blastocoel to the outside
at the lower or entoblastic pole—a remarkable phenomenon
already observed by Kleinenberg. This pore is formed by the
separation of the larger cells during the active periods of division,
now very marked, which alternate with equally marked quies-
cent stages. I have never found a trace of the pore during the
quiescent periods, but it is certainly present in more than one
of the active periods. (Compare Figs. 22 and 26.) It seems
probable therefore that it appears in several successive active
periods, closing in the succeeding quiescent periods. The only
explanation of it that occurs to me is that it may serve as a
channel for the expulsion or entrance of liquid during the active
stage, so as to avoid undue pressure on the cells during their
change of form.

IV. GASTRULATION.

A modified embolic invagination takes place in the course
usually of the third day, though the rate of development varies
so greatly with the temperature and differs so widely among
individuals that no general statement of the time has any value.
The spherical blastula becomes flattened and slightly elongated
(Figs. 31, 32), finally assuming the form of an oval plate with
rounded edges (Figs. 33, 34, 39, 40). During this general
change of form the cells undergo striking alterations. The
larger cells of the lower pole become clearer, assume a columnar

400 WILSON. [Vot. III.

form, and arrange themselves in a perfectly flat plate, their
nuclei remaining near the peripheral ends. The smaller cells
of the upper pole become greatly flattened and spread out, so as
to form a pavement epithelium covering the plate of larger cells
above and on the sides. The primary mesoblasts lie side by
side near one end, closely surrounded by the outer cells, and
from each a somewhat irregular row of cells extends downwards
and forwards. The cleavage cavity is much reduced, but does
not disappear until a little later.

The embryo is now bilaterally symmetrical, with well-defined
dorso-ventral and posterior axes, and, except for the precocious
development of the mesoblast, is closely similar to the ‘“ Pla-
kula”’ of Biitschli. The germ-layers are perfectly differentiated,
the entoblast occupying the entire ventral surface, the ecto-
blast covering the sides and dorsal surface, while the mesoblast
is arranged in two diverging rows that lie near the sides of the
embryo and meet each other in the median line behind. Series
of sections through such embryos (see Figs. 45, 46), as well
as optical sections of entire embryos (Figs. 35, 42), show in
the clearest manner that the mesoblastic rows end abruptly
in front at the sides, without extending across the median line.
At a much later period they grow forward and join above the
mouth, this forward growth being effected in the main by an
actual migration of the cells, and in no case by proliferation
from either ectoblast or entoblast.

The embryo now becomes concave on its lower side, so as
to form a large blastopore occupying the entire ventral aspect
(Fig. 35). By the folding in of its sides this blastopore then
assumes the form of a longitudinal slit (Fig. 37), and rapidly
closes from behind forward, the anterior part remaining open as
the mouth (Figs. 36, 42). During these changes the anterior
lip of the blastopore undergoes no change; the general history
of the blastopore is, therefore, closely similar to that Ewpomatus,
as described by Hatschek (No. 23). The anus is not formed
until the end of larval life.?

1 There is a considerable variation in the closure of the blastopore, owing to differ-
ences in the rate of folding between the sides and the posterior margin of the blasto-
pore. Asa rule the sides fold in more rapidly than the hinder lip, thus giving rise to
a slit-like blastopore, but in some cases the reverse is true, so that the blastopore
never appears as a slit, but always as a rounded opening.

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 4OI

V. GENERAL HISTORY OF THE GERM-BANDS,

I shall use the term germ-band to mean the composite struc-
ture extending along either side of the body from the primary
mesoblast to the dorsal side of the mouth, and consisting in its
middle portion of the three strata of cells referred to at p. 389.

1. The Mesoblast. —In its earliest form, as it occurs in the
blastula, each germ-band consists only of the primary mesoblast
with the corresponding row of mesoblastic cells extending
forwards from it and joining its fellow in front (Figs. 30, 31,
32). As the blastula flattens shortly before the invagination,
the mesoblastic rows are carried out towards the sides of the
embryo and their anterior ends become widely separated. As
the invagination proceeds the mesoblastic rows undergo a two-
fold change. First, they grow forward and upwards, as already
described, so as to approach one another above the anterior lip
of the blastopore (Fig. 43); and second, their middle portions
are carried still further downwards so as to lie on the ventral
side, though they are still widely separated. Meanwhile the
ectoblast becomes thickened immediately over the mesoblastic
cells and thus forms the outer or ectoblastic stratum of the
band. This thickened area of the ectoblast everywhere accom-
panies the underlying mesoblastic band, but is somewhat wider.
Dorsally and ventrally it passes rather suddenly into the large-
celled, flattened epithelium that forms the upper and lower in-
vestment of the embryo (Fig. 41). Sections at this stage show
the ectoblast to be still everywhere composed of a single layer
of cells. In front the thickened ectoblastic areas fade away into
the pavement epithelium of the dorsal surface (surface views in
Figs. 33, 35, 36, 41, 43; sections in Figs. 52, 53, 67,68; see ex-
planation of plates).

It is necessary to refer at this point to the group of enlarged
ectoblastic cells known as “ Schluckzellen,’”’ which appear at an
early stage at the anterior part of the body in the embryos of
some Hirudinea, and in a number of the Oligocheta, including
some species of Lumbricus. These cells, whose mode of origin
has been carefully studied by Hatschek in Criodrilus (No. 18),
and by Vejdovsky in a number of Oligochzeta (No. 46) have
been shown by the last-named author to be larval excretory
organs. They are at first enlarged ectoblast cells which lie at the

402 WILSON. [Vot. III.

surface and form the dorsal lip of the blastopore; at a later
period they are overgrown by the ectoblast and thus come to lie
between the ectoblast and entoblast in the median dorsal line.
This account of their position and mode of origin holds true for
Lumbricus communis and Lumbricus terrestris, but in Lumoricus
fetidus, the form which I have most carefully studied, they
appear to be wholly wanting (see p. 422). In this species the
dorsal lip of the blastopore is formed by large entoblast cells
covered dorsally by flattened cells of the ectoblast (Figs. 35, 46).

As development proceeds the lateral areas of thickened ecto-
blast extend forwards until they meet above the blastopore, the
“ Schluckzellen”’ (in LZ. communts and L. terrestris) being thus
covered and pushed somewhat backward. At a slightly later
period these ectoblastic bands extend ventrally around the blas-
topore until they meet and quite enclose it on the ventral side
(Fig. 43). The thickened ectoblastic lips thus formed now grow
into the blastopore to form the stomodzeum which is in this man-
ner fully established very soon after the narrowing of the blasto-
pore. The opening into the archenteron appears never to close,
and even before the establishment of the stomodazeum the embryo
begins to swallow the albumen in which it floats.

The middle stratum of the germ-bands can first be distin-
guished while the embryo is still nearly spherical, immediately
after the establishment of the stomodzum. At this period
close examination of the surface of the bands near their middle
part shows some of the ectoblast cells to be arranged in distinct
longitudinal rows, each one of which terminates posteriorly in
a larger cell or teloblast (Figs. 47, 49; and Plate X1X.). Sec-
tions at this stage show that the cells of these rows, and the
teloblasts at their extremities, form a part of the general ecto-
blast, though here and there they are overlapped by the adjoin-
ing cells, and in some cases may be actually covered (Figs. 53,
54, 66-68). In later stages the teloblasts and corresponding
cell-rows gradually sink below the surface and thus give rise to
a stratum of cells lying between the mesoblast and the outer
ectoblast, but imbedded in, and clearly forming a part of, the
latter (Figs. 70, 71, 72). Their precise mode of origin and
ultimate fate are described further on.

The germ-bands are now fully established, and their sub-
sequent general development may be briefly sketched as follows:

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 403

The embryo rapidly elongates, becoming successively ovoid, elon-
gate, and finally vermiform. Upon the full establishment of
the germ-bands the teloblasts and cell-rows have a definite
and characteristic arrangement which is retained throughout
the development. This arrangement (Figs. 47, 48, 49, 63) is
essentially the same in the three species of Luméricus I have
examined, and an exactly similar arrangement exists in the
embryos of a small fresh-water Oligochzte which I have unfor-
tunately not been able to determine, but which is almost cer-
tainly not Lwmbricus. The primary mesoblasts lie behind and
somewhat above a horizontal plane passing through the middle
of the body (Fig. 38), in contact with each other in the median
line. New cells are always formed at the postero-lateral angles
of these teloblasts (Fig. 60), and the mesoblastic rows curve
thence forwards and downwards around the teloblasts, nearly
or quite meet in the middle ventral line, and then pass outwards
and forwards, soon widening into a pair of flattened plates in
which the coelomic cavities are developed long before their
concrescence on the ventral side (Figs. 63, 69). The neuroblasts
are much further forwards than the mesoblasts, and le just
opposite the lower (mediad) edge of the mesoblastic plate. The
two nephroblasts lie side by side somewhat further back and
a little towards the dorsal side. The lateral teloblast, which
I have found in early stages of L. communis only, lies just in
front of the nephroblasts opposite the upper edge of the mes-
oblastic plate (Figs. 61, 67).

The growth of the germ-bands keeps pace with that of the
embryo generally. The teloblasts are carried steadily backward,
each leaving behind it a trail of cells derived partly by continual
divisions of the teloblast, partly by subsequent divisions of the
cells thus formed. After the most careful study of a large
number of germ-bands in surface view, and in transverse and
longitudinal sections, I can state positively that the several cell-
rows — mesoblastic, neural, nephric, and lateral —are wholly
derived from the corresponding teloblasts, and in no other way.
I have repeatedly observed all stages of division in all of the
teloblasts, in the cells derived from them, and in the outer ecto-
blast. The division-figures prove beyond question that the cell-
rows elongate in the manner described, and I have never seen
the least indication of any other mode of increase.

404 WILSON. [Vo. III.

In early stages all the cell-rows are but one cell in width at
their hinder ends. Passing forwards they soon become several
cells wide and deep, and the two nephric rows on each side fuse
completely. Only the neural and the mesoblastic rows can be
traced around the mouth; the others fade away at the sides of
the stomodeum. As the embryo enters the later stages of
development the teloblasts break up into smaller cells, so that
each cell-row, now several cells in width throughout its whole
length, terminates behind in a group of undifferentiated cells
(Figs. 63,97). The neuroblasts, nephroblasts and lateral telo-
blasts first disappear ; the primary mesoblasts persist to a much
later period, and only disappear near the time of hatching, when
the proctodzeum is formed.

Concrescence of the bands begins in front and proceeds
thence regularly backwards, the union of the bands taking place
first in the median ventral line, afterwards in the median dorsal
line, as the mesoblastic bands extend around the archenteron.
It begins at a very early period, as already described, with the
anterior fusion of the ectoblastic part of the bands to form the
stomodzeum. The mesoblastic bands move together at a much
later period. As the bands come together the neural rows of
the two sides come into contact in the middle line, fuse more
or less completely together, and thus give rise to the ventral
nerve-chain. Posteriorly the bands diverge up to a very late
stage of development, having the disposition shown in Fig. 63.
Owing to this divergence and the subsequent junction of the
bands at the extreme posterior end, a somewhat elongated space
is enclosed by the hinder part of the bands, in which the ecto-
blast and entoblast are directly in contact.

From the foregoing account it will be seen that the cephalic
lobe (prostomium, or head) arises by concrescence of the an-
terior extremities of the same germ-bands that form the trunk.

A more detailed account of the formation of the head is given
at page 407.

VI. GENERAL HISTORY OF THE MESOBLAST.

1. General Differentiation. — The forward growth and union of
the mesoblastic bands to form the cephalic mesoblast has already
been described. Upon the completion of this process the meso-

No. 3.] ZHE EMBRYOLOGY OF THE EARTHWORM. 405

blastic bands form a complete ring which encircles the archen-
teron longitudinally with its middle part drawn somewhat
towards the ventral aspect. Posteriorly the bands are a single
cell in width ; anteriorly they soon widen into flat plates which
are widest in the middle region, narrowing somewhat as they pass
upwards at the sides of the stomodzeum. It should be borne in
mind that the cephalic mesoblast (which forms the anterior
median portion of this ring) is formed mainly by an actual migra-
tion of cells from the anterior ends of the mesoblastic bands.
At a somewhat later period some of the cells situated at the
edges of the mesoblastic bands lose their connection with the
others, pass upwards between the ectoblast and entoblast, and
thus give rise to what I have called at page 389 the mzgratory
mesoblast ; the remaining portion of the mesoblastic bands (in
which the coelomic cavities afterwards appear) constituting the
“trunk-mesoblast.” Anteriorly the migratory mesoblast of the
trunk-region is continuous with the cephalic mesoblast (Fig. 50) ;
toward the ventral side it passes suddenly into the mesoblast of
the germ-bands.

The cells of the migratory mesoblast do not form a continu-
ous layer, but remain scattered, become branched, and form a
beautiful network (Fig. 89) that encloses the entire archenteron.
In this network at least two kinds of cells can be distinguished.
The first are enormously long branching muscle-fibres arranged
in a longitudinal and a circular set which cross at right angles
and form an open network. The substance of the fibres stains
deeply with haematoxylin and is nearly homogeneous; the nu-
cleus is situated near the middle of the fibre, attached to its
side, and surrounded by asmall quantity of granular protoplasm.
The fibres are sometimes simple, but more usually subdivide
towards their extremities into excessively fine twigs, and occa-
sionally a cluster of branches is given off near the middle of
the fibre at right angles to its general course. The granular pro-
toplasm surrounding the nucleus in some cases also gives off
branches, but these are easily distinguishable from the muscular
branches.

Cells of the second kind are much less numerous than the
others. They are granular branching cells having the general
appearance of large connective-tissue cells. In some cases their
branches appear to join those of other similar cells and the pro-

406 WILSON. (Vo. III.

toplasmic branches of the muscle-cells, but I have not fully
satisfied myself on this point. JI have searched in vain for
nerve-cells in this network.

The migratory mesoblast of- the trunk-region is gradually dis-
placed by the trunk-mesoblast of the germ-bands, which as de-
velopment proceeds, steadily extends both dorsally and ventrally,
forcing its way between the ectoblast and entoblast as it grows.
The two bands finally meet and fuse with one another, first along
the median ventral line from before backwards, subsequently
along the median dorsal line in a similar manner. From it (v.
znfra) are developed the permanent muscles of the trunk, which
are differentiated from the mesothelial walls of the ccelomic
cavities and are unbranched (as may be clearly seen in prep-
arations macerated in Hertwig’s fluid). The longitudinal fibres
are the first to appear, forming on each side a longitudinal bun-
dle that lies just opposite the boundary between the nephric
and neural cords (Figs. 72, 90, 91). A second bundle appears
later just outside the nephric cord. I have been unable to deter-
mine whether the larval branching muscle-fibres disappear or
remain embedded in the adult body-wall.

In the head-region the mesoblastic cells become amceboid and
branched and ultimately arrange themselves so as to enclose a
single median cavity (prostomial or head-cavity) traversed by
branching contractile cells.

From the foregoing account it appears that the trunk-meso-
blast is a “mesothelium,” the migratory mesoblast of the trunk
a typical ““mesenchyme,” while the cephalic mesoblast is of an
intermediate character. All these cells have, however, a common
origin, and the distinction between “mesothelium ”’ and “ mesen-
chyme” in the embryo as originally made by the Hertwigs (No.
25) is here of wholly secondary importance (as has been shown
to be the case in other annelids by Kleinenberg and Hatschek).
The migratory mesoblast of the trunk appears to be a special
larval musculature precociously developed in order to enable the
embryo to manage the enormous mass of albumen with which
its body is distended.

2. Origin of the Celom. — The trunk-cavities appear in the
mesoblastic bands in regular succession from before backwards
(Figs. 50, 63, 97). In longitudinal sections the bands are seen
to be posteriorly but one cell in thickness; further forward

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 407

they are arranged in two layers which still further forward are
seen to be the somatic and splanchnic layers, the coelom appear-
ing between them. Posteriorly the cells of these layers have
a pyramidal form and dove-tail together with great regularity.
Further forward, as they separate, the narrow inner overlapping
ends of the cells remain in contact, the coelomic cavities appear-
ing as spaces between them, so that each cell forms part of a
dissepiment. The number of cells rapidly increases, however,
as the coelomic cavities enlarge, so that the dissepiments, which
are at first in contact above and below, are separated by the
somatic and splanchnic epithelium, and also become two-layered.

The cavities of the two bands are at first wholly separate,
since they make their appearance some distance behind the point
of concrescence, as shown in Fig. 69. As the bands grow to-
gether the corresponding cavities of the two sides are opposed to
one another and finally fuse, at first incompletely on the ventral
side where a ventral mesentery persists, afterwards completely
on the dorsal side, so as completely to surround the archenteron.

The most anterior pair of cavities (see Fig. 50) lie at the
sides of the stomodzum, bounded in front by a mesoblastic
wall which at first is horizontal, but subsequently becomes
oblique and finally vertical. These cavities give rise to the coclom
of the first post-oral somite, in which nephridia never develop.
The following pair of cavities give rise to the second somite,
which has no nephridia of its own, but receives the funnels of
the following or third somite. The first pair of setigerous
glands are developed in the second somite.

The head-cavity appears in the middle line above the stomo-
dzeum at about the same period as the anterior pair of trunk-
cavities, directly between which it at first lies. Series of sec-
tions in all planes show most clearly the unpaired character of
the head-cavity from its first appearance onward. Its walls are
bounded by a distinct layer of mesoblastic cells, and its cavity
is traversed by a loose network of branching contractile cells.
On the dorsal side these cells are continuous posteriorly with
the migratory mesoblast of the trunk, and the head-cavity itself
appears to be continuous with the lacunz between these cells.
In later stages, however, as the trunk-mesoblast extends around
the dorsal side of the archenteron, the head-cavity acquires a
definite hinder limit, formed by the dorsal union of the first pair

408 WILSON. [Vot. III.

of dissepiments (Fig. 80). Into this cavity projects the foun-
dation of the cerebral ganglia, which is covered inwardly by a
layer of mesoblast.

In passing from above downward in a series of horizontal
sections the prostomial cavity first appears (Figs. 55 and 56), and
then a little further down the anterior pair of coelomic cavities
come into view at the sides of the stomodzum. In slightly
later stages all three cavities may be seen in one section, as
shown in Fig. 58. I find it difficult to understand Kleinenberg’s
account of the matter, and am forced to conclude that the two
lateral cavities by the fusion of which he supposed the pro-
stomial cavity to arise, are simply the anterior pair of trunk-
cavities, and that he overlooked the partition separating them
from the median cavity. Their true relations will be made
clear by comparison of Figs. 50, 57, and 58.

3. Blood-Vessels.— The first blood-vessel to appear is the
ventral or sub-intestinal. It makes its appearance in the median
ventral line, shortly after the fusion of the mesoblastic plates in
this region, as aspace lying between the wall of the archenteron
and the mesoblast (Fig. 72). At first it has no proper wall,
being bounded below by the mesoblast and above by the ento-
blast, so that it would seem to represent a part of the original
cleavage cavity. Here and there along its course, however, a
single cell can be seen on its dorsal side applied to the ento-
blast. In later stages— or what amounts to the same thing,
further forwards —these cells increase in number, so that the
vessel becomes enclosed in a distinct wall of its own and appears
to lie in the splanchnic mesoblast as figured in Fig. 25 a, Pl. XI.
of Kleinenberg’s paper. The most careful examination has
failed to satisfy me as to the precise origin of the walls of this
vessel. But without being able to give absolute proof, I believe
them to arise from cells which migrate out of the mesoblast.
In any case the cavity of the vessel would seem to be of the
same character as the lacunar cavities between the cells of the
migratory mesoblast, which are for a time at least in connection
with the head-cavity.

As to the development of the dorsal vessel, I can do little
more than confirm Kowalevsky’s interesting discovery (after-
wards extended by Vejdovsky to Criodrilus, No. 43) of its double
origin. Shortly after the appearance of the ventral vessel two

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 409

lateral vessels make their appearance near the outer or dorsal
edge of the mesoblastic plate (Fig. 72). They develop in pre-
cisely the same way as the ventral vessel, first appearing as
spaces between the splanchnic mesoblast and the archenteric
wall, but ultimately acquiring walls of their own.

In the posterior region these vessels lie parallel to the ventral
vessel, quite on the ventral side of the embryo. On tracing them
forwards they are found to assume a lateral position, and finally
to pass towards the dorsal side, where they finally unite in a
single vessel which runs forwards in the median line (Fig. 51).

The arrangement of the longtitudinal trunks at this period is
almost precisely like that of many adult tubicolous Polychzeta
(Amphitrite, Melinna, Lantice; see Meyer, No. 35, Taf. 23); and
Beddard (No. 4) has shown that the dorsal vessel remains more
or less completely separated into two parallel trunks in a number
of Oligochzeta (Megascolex, Microcheta, Acanthodrilus). Bed-
dard is inclined to consider this the primitive mode of develop-
ment — a view which, however, seems at present to rest on in-
sufficient evidence.

The dorsal vessel is formed by the progressive backward
concrescence of the two lateral vessels —a process which on the
whole keeps pace with that of the mesoblastic bands and is only
finally completed near the time of hatching. The vessels lag
somewhat behind the remaining mesoblast, however, so that in
the posterior region they still lie at the sides when the mesoblast
has entirely surrounded the archenteron, as in Fig. 72, Pl. XX.
The cells of the mesoblast lying above the lateral vessels seem
to pass upward in large part by migration, and only become
arranged in definite somatic and splanchnic layers at a later
period.

The first of the circular vessels to appear are the circum-
cesophageal vessels or pseudo-hearts, which are developed in
the splanchnic mesoblast in connection with the unpaired an-
terior part of the dorsal vessel, and as far as I have been able to
observe are surrounded with definite walls, from the start. The
circular intestinal vessels develop considerably later, and I have
never been able to distinguish them until after the complete
fusion of the lateral longitudinal trunks to form the median
dorsal vessel.

410 WILSON. [Vo. III.

VII. Tue ENTOoBLAST.

Just before the invagination of the gastrula the entoblast
forms a flat plate of prismatic cells covered dorsally by the
mesoblast and the thinned ectoblast, and at the sides by the
mesoblastic bands and the thickened areas of the ectoblast.
The nuclei lie near the lower ends of the cells (Figs. 34, 45).
During the invagination the anterior edge of the entoblastic
plate remains stationary, while the lateral margins bend down-
wards and the posterior margin grows forward. The superjacent
ectoblast takes part in this change, but the thickened areas
overlying the mesoblastic bands are left behind, so that the
archenteron is covered below with very thin large polygonal
cells (Figs. 36, 41, 42). At the completion of the invagina-
tion the archenteron has a nearly spherical form (Fig. 38). Its
cells are clear, columnar, with their nuclei near the inner ends.
As soon as the embryo begins to swallow the albumen, which is
done almost immediately after the narrowing of the blastopore,
the whole body becomes greatly distended and enlarged, so that
the archenteric wall becomes much thinner and the cells undergo
a marked alteration in form. Their cell substance also changes
in character, the protoplasm now containing numerous slightly
staining globules of various sizes. I am unable to explain by
what process absorption takes place ; the appearances indicate
that the albumen is taken bodily into the cells, amceba-fashion.

The ingrowth of the stomodzeum and the concomitant increase
of the mesoblast in the anterior region cause still further changes
in the form of the archenteron. The stomodzum grows back-
wards and downwards in the median line (see p. 25), pushing
the archenteric wall before it, while the pressure within the
archenteron causes it to bulge forward into the head-cavity,
which is thus often almost or quite obliterated. In early stages
this forward bulging is often so extreme as to cause the mouth
to face directly downwards.

The later changes may be very briefly treated. The archen-
teron continually elongates with the growth of the body, its
hinder extremity remaining in contact with the ectoblast just
behind the primary mesoblasts, at which point the stomodzeum
is afterwards formed ; in front the archenteron becomes widely
separated from the extremity of the body, owing to the elongation

No.3.] ZHE EMBRYOLOGY OF THE EARTHWORM. 4II

of the stomodzeum and the growth of the anterior somites (Fig.
50).

The ingrowing stomodzum (see following section) pushes
the archenteron backwards as far as the sixth somite, which is
its extreme limit in the adult and marks the point of union of
the pharynx and the cesophagus. Thus the cesophagus is lined
by entoblast, as are also the calciferous glands which develop
as diverticula from it. At the time of hatching the various
regions of the alimentary canal are completely differentiated,
and the typhlosole is established as a deep infolding of the
dorsal median wall of the intestine. I have not yet attempted
to follow in detail the histological differentiation of the ali-
mentary wall.

VIII. THe EcrospraAst’anp ITs) PRODUCTS.

1. The origin of the general ectoblast of the ectoblastic stra-
tum of the germ-bands and of the stomodzeum have already been
described. At the end of the gastrulation the ventral aspect of
the embryo is covered by a large-celled pavement epithelium
which passes abruptly at the sides into the swollen superficial
granular cells of the germ-bands. A little later some of the
cells along the median ventral line become enlarged and covered
with short cilia which cause the embryo to rotate slowly in the
longitudinal vertical plane. The ciliated cells are at first arranged
in a single irregular series along the median line, and the indi-
vidual cells are separated from one another by groups of smaller
non-ciliated cells. Ata later period the ciliated cells come into
contact and form an irregular continuous double row which form
the floor of a slight but distinct ventral groove. In front this
groove nearly disappears, but the ciliated cells are continuous
with the ventral lip of the stomodzeum, and the cilia extend
around the lips of the stomodzeum into its cavity. In still later
stages the ciliated cells gradually disappear, apparently by break-
ing up into ordinary ectoblastic cells and losing their cilia. I
am certain that they take no part in the formation of the ventral
nerve-chain, which is entirely formed by concrescence of the two
neural rows. As the germ-bands spread around the body, the
pavement-epithelium of the dorsal and ventral surfaces is grad-
ually converted into a columnar epithelium which persists as the
hypodermis and is covered by the cuticle.

412 WILSON. [Vot. III.

2. Stomodwum. — The foundation of the stomodzeum by con-
crescence of the ectoblastic layer of the germ-bands has already
been described; its late development is shown in Figs. 79-82.
As the stomodzeum grows in, its cells become ciliated, consider-
ably enlarged, and their substance becomes extensively vacuo-
lated. Somewhat later the walls of the stomodzeum become
several cells deep, consisting of a deeper stratum of small gran-
ular cells and an irregular superficial stratum of clear ciliated vac-
uolated cells, which are often dovetailed in with the smaller cells,
but sometimes lie flat on their outer ends. Still later the larger
cells disappear completely, and the stomodzeum consists only of
columnar, granular cells derived from the smaller deeper cells.

The stomodzum grows inwards exactly between the meso-
blastic cavities of the first somite (which li at its sides), and ven-
tral to the head-cavity. It grows thence backwards as far as the
dissepiment between the fifth and sixth somites, where its limit
can be distinctly made out in vermiform embryos 15 mm. long
and nearly ready to hatch. In such embryos the circum-ceso-
phageal vessels are fully established, so as to show clearly the
limit between the pharyngeal and cesophageal regions. The first
aortic arch, which is smaller than the following ones, is found
in the sixth somite, immediately behind the limit of the stomo-
dzum. It is clear therefore that the stomodzeum gives rise
only to the pharynx, and that the cesophagus, with its calciferous
glands, is derived from the archenteron, —a result in accordance
with Vejdovsky’s account of the stomodzum in Rhyuchelmts
(No. 44, p. 100). In front of the sixth somite the dissepi-
ments break up more or less completely to form a mass of
radiating fibrous structures which suspend the pharynx in a
large irregular cavity which extends forward about to the second
somite. Still further forward the ccelom is wholly obliterated,
being filled, like the prostomial cavity, with a spongy mass of
muscles, connective tissue, vessels, and nerves.

I may at this point conveniently speak of the change of posi-
tion which the cephalic ganglia undergo during the differentia-
tion of the stomodzum. When first formed, these ganglia lie,
as we have seen, at the extreme anterior part of the body in
the prostomial cavity. But as the stomodzeum grows inwards the
ganglia travel gradually backwards until they come to lie in the
third somite in the anterior extremity of the ccelom. From

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 413

them the cesophageal commissures pass nearly vertically down-
wards to the sub-cesophageal ganglion, which likewise lies in the
third somite! (see p. 417).

The stomodzeum of ZL. fetzdus differs remarkably from that of the other
species studied. In Z. terrestris and L. communis the invaginated ectoblast
is but slightly thickened and is directly continuous with the general ectoblast.
In L. fetzdus, on the other hand, the ventral lip of the stomodzeum becomes
expanded like a funnel, and greatly thickened, especially towards the sides,
so as to form a swollen mass of elongated fusiform cells which in sagittal sec-
tions (Fig. $2) is strikingly like a taste-bud. This mass (which seems to
correspond to the ‘*‘ Mundwulst” of Crzodrzlus) is transversely elongated so
as to form the entire ventral lip of the stomodzum. In some cases it is
slightly bilobed, but usually is nearly uniform in thickness. The cells are
attenuated towards their outer ends, and the peripheral ones are curved so as
to bring the ends of all the cells together at the surface. Ventrally the cells
of the stomodzal lip abut against those of the ventral ectoblast, from which
they are separated by a very distinct line of demarcation. Inwardly they are
also separated, though less markedly, from the cells of the narrow part of the
stomodeum. The cells of the thickened lip are slightly granular, but not
more so than those of the inner part of the stomodzum; their nuclei are
large and conspicuous. In later stages the thickening gradually disappears
and its cells appear to be converted into ordinary columnar epithelial cells like
those forming the general wall of the stomodzum.

Iam unable to say whether this larval structure is to be regarded as a
glandular or a sensory apparatus. It suggests in its structure, position and
mode of origin the paired larval sense-bulbs, or primary sense-organs of the
lip found in the Hirudinea (see Whitman, No. 52, p. 159), which by fusion in
the middle line would give rise to precisely such a thickened lip. Moreover,
Hatschek figures (No. 18) the ‘“*Mundwulst” of Crzodrdlus as arising from
completely separate foundations. On the other hand, it is difficult to un-
derstand the use of so highly developed a sense-organ in but one species of
Lumbricus, and its presence is so obviously correlated with the peculiar char-
acter of the albumen in Z. fetzdus, that I am inclined to regard it as a larval
digestive gland. It will be remembered that in this species the albumen is
tough and jelly-like, differing markedly from the slimy, mucus-like albumen of
other forms. It seems therefore not unlikely that the cells of the organ in
question may pour forth a secretion to soften the albumen and thus facilitate
its ingestion by the young embryo.

In LZ. communis and terrestris there is no indication of this structure at any
period. In both these species, however, peculiar deeply staining gland-like
cells are found in the anterior part of the stomodzum (see Fig. 81), lying for
the most part in its ventral wall, but also extending up on the sides, in some
cases reaching the dorsal wall. These cells may perhaps be of the same na-

1 This backward shifting of the cephalic ganglia is characteristic of many Oligo-
cheta. See Vejdovsky, No. 44.

414 WILSON. [ VOL. ET

ture as the “ larval gland-cells ” of Clepszne (Whitman, No. 52, p. 157), though
they are not pigmented and have a somewhat different position.

The later differentiation of the pharynx is effected by an enormous thicken-
ing of its mesoblastic investment on the dorsal side, the ventral mesoblast
remaining extremely thin.

3. Proctodeum.— The proctodzum is very long delayed in
development, only making its appearance near the end of feetal
life, when the body has an elongated form and concrescence of
the germ-bands is nearly complete. It is formed as a hollow
invagination of ectoblast which pushes its way between the
hinder ends of the mesoblastic bands, and soon fuses with the
archenteric wall. I have not been able certainly to determine
the important question of its precise morphological relation to
the ends of the germ-bands, owing to the fact that before its
formation the primary mesoblasts break up into smaller cells
and thus render the hinder limits of the bands somewhat diffi-
cult to determine. In Polygordius, and many other annelids,
the proctodzum is formed behind, or dorsal to the primary
mesoblasts, z.e. outside the mosoblastic ring formed by the
germ-bands; and this seems to be the typical position of the
anus in annedids generally. In Lwmbricus towards the end of
foetal life the primary mesoblasts break up intoa group of cells
from which the mesoblastic bands (now entirely united along
the ventral line) extend forward (Fig. 97). As the proctodzum
grows inwards this mass of cells grows upwards at the sides of
the proctodzeum in two horns, which finally unite in the dorsal
line above it (cf Figs. 95-97). Thus the mesoblastic ring ulti-
mately comes to surround the proctodzeum behind, as it does at
a much earlier period the stomodzeum in front, the middle por-
tion of the ring having meanwhile undergone concrescence
throughout its whole extent. The stomodzeal invagination has
the form of a longitudinal slit which at first faces upwards
owing to the curvature of the body, but gradually is turned back-
wards as the body straightens out. Its walls fuse completely
with those of the archenteron and assume the same histological
character, and every trace of the limit between them disappears.
It is therefore impossible to determine how far forward the
proctodzeum extends, but its extent is certainly very limited.

No: 3.) THE ZMBRYOLOGY OF THE EARTHWORM. 415

IX. Nervous SYSTEM.

Apart from the discovery of the neuroblasts my results on the
origin of the nervous system differ materially from those of
Kleinenberg, and have, as I believe, an important bearing on
the question as to the relation between the head and the trunk.
Two principal questions are involved, namely: (1) do the cere-
bral ganglia arise independently of the ventral chain, and (2) do
they arise from a median unpaired apical plate (Scheitelplatte) ?
As far as Lumbricus is concerned both these questions must be
answered in the negative. My preparations show clearly, I
think, that the entire nervous system has a double (bilateral)
origin and is formed by a process of concrescence; and further-
more, that the foundation of the cerebral ganglion of each side
is simply the thickened anterior extremity of the corresponding
neural row.

In its first recognizable condition the nervous system is rep-
resented (Fig. 47) by a short neural row lying at the surface of
the germ-band on each side the body. Each row terminates
behind in a neuroblast; anteriorly it passes up at the side of the
mouth and is apparently lost in the general ectoblast. Its struc-
ture in front can only be made out by the study of oblique lon-
gitudinal sections passing in such a plane as to cut the neural row
lengthwise (z.¢., a longitudinal plane inclined about 45 degrees
to the sagittal plane). After many unsuccessful attempts I suc-
ceeded in securing such a series, consisting of 27 consecutive
sections through an embryo slightly older than that shown in
Fig. 47. This series shows the relations so clearly and is of
such importance that I figure six of the sections (Plate XX.,
Figs. 73-78).

Figure 73 is the uppermost, z.¢., the one nearest the surface.
It passes lengthwise through the posterior part of the germ-
bands, cutting the primary mesoblast at J/, the right neuroblast at
Vb, and showing the connections of these teloblasts with the cor-
responding rows. The succeeding sections pass at successive
lower levels, and, owing to the curvature of the germ-bands, show
the forward continuation of the bands. Figure 74 is the section
adjoining Fig. 73; it shows the neural row ze passing forwards
and upwards at the surface of the body. Figure 75, two sections
further on, is of great importance. It shows that the neural

416 WILSON. [Vo. III.

rows (which here represent the future cesophageal commissures)
are partly covered in at the sides by the general ectoblast, and
that their extreme anterior ends are enlarged and partially united
with the dorsal ectoblast to form the foundation of the cephalic
ganglia. This section shows also the beginning of the migration
of the anterior mesoblast cells to form the cephalic mesoblast.
Figure 76 is a more enlarged view of part of the adjoining sec-
tion to show the continuity of the neural row with the cephalic
foundation. Figure 77 is four sections further along, and shows
the complete disappearance of the neural rows towards the me-
dian line. Figure 78, four sections further on, passes in front
through the median line, and shows the mouth-cavity, the group
of “ Schluckzellen”’ which forms the anterior limit of the mouth
and were visible already in Fig. 77, and the large ciliated cells of
the median ventral surface. In sections at a still lower level (z.2.,
on the left of the median line) the neural and mesoblastic bands of
the left side appear in oblique section. This clearly demonstrates
the fact that at this period, although the gastrula ts fully estab-
lished, the germ-bands are completely separated in front. The
series shows furthermore that there is no apical neural plate, the
cephalic ganglia arising independently on either side of the me-
dian line. It shows finally the important fact, that the cephalic
ganglia arise from the same neural rows that give rise to the
cesophageal commissures and the ventral chain, though their
development is slightly in advance of the other parts (see p. 434).

At a slightly later period the mesoblastic, neural, and ecto-
blastic elements of the opposite sides of the body grow together
in the median dorsal line above the mouth (cf Fig. 43.), and the
unpaired cephalic cavity appears just between the two cephalic
ganglia (Fig. 56). At this period a bridge of neural tissue,
closely united with the ectoblast, can be traced across the me-
dian line from one cephalic ganglion to the other (Figs. 55, 56).
I have not certainly determined whether this bridge is formed
by proliferation of the overlying ectoblast or by growth of the
neural structures already existing. I incline, however, to the
former view, because there appears to be a complete fusion of
the neural tissue with the ectoblast in the middle line.

The question whether the cephalic ganglia, like those of the
ventral chain, are derived from the neuroblasts or by prolifer-
ation from the general ectoblast, still remains in doubt. This

No.3.) ZHE EMBRYOLOGY OF THE EARTHWORM. 417

question, however, appears to be largely one of terms only, for
both the neuroblasts and the neural cells form at this period
part of the general ectoblast (Figs. 53, 73), and all the cells
are constantly undergoing division. The fact that the neuro-
blasts, when first distinguishable, lie some distance behind the
mouth, seems to indicate, however, that the cephalic ganglia and
the cesophageal commissures are first differentiated zz sztu
directly out of the ectoblast, and that the neuroblasts are after-
wards differentiated as special centres of apical growth as the
embryo begins to elongate.

Soon after their union the cephalic ganglia project into the
prostomial cavity, and become surrounded by a mesoblastic in-
vestment. As the stomodzum grows inward, these ganglia, as
well as the commissures extending around the cesophagus, are
carried backwards until they lie in the third somite, which is
their permanent position (cf Figs. 50, 51, 79, 81).

The ventral chain arises entirely by concrescence of the two
neural cell-rows, a process which has been accurately described
by Kleinenberg. I have sought in vain for any indication of the
participation of a median element (‘ Mittelstrang”’) in the forma-
tion of the nerve-cord. The lateral nerves are formed as out-
growths from the ganglionic cord.

Concrescence of the neural rows begins in the first somite im-
mediately behind the lower lip, where a slight ganglionic swell-
ing is formed. A second more distinct double swelling is found
in the second somite, a third in the third somite, and so on through
the body. As the cerebral ganglia travel backwards in the man-
ner described above, the ganglia of the first three somites fuse
completely together to form the ganglionic mass known as the
suboesophageal ganglion, which would therefore seem to repre-
sent three pairs of ganglia. Itis, however, possible that the orig-
inal anterior enlargement in the first somite is not morphologi-
cally to be regarded as a ganglion.

A careful study of cross-sections of the neural cords along
the region of concrescence brings out the fact that the gangli-
onic regions are the first to unite, and that they can be distin-
guished as enlargements of the neural cords before concrescence
begins; z.e. behind the point of union. Figures 90 and 91, PI.
XXIL., illustrate this point. The former, which is taken through
the region of the commissures, shows the neural cords perfectly

418 WILSON. [Vot. III.

separate. The latter, two sections further back, passes through
a ganglionic region and shows the enlarged cords joined by a
narrow transverse bridge of neural tissue. This alternate sepa-
ration and junction of the neural cords can be traced for a con-
siderable distance behind and in front of the sections figured.
All my preparations indicate that the transverse bridge of tissue
uniting the ganglia is a product of the neural cords and has no
connection with the superficial ectoblast.

I can add little to Kleinenberg’s account of the histological
differentiation of the ventral cord. The fibrillar substance
appears some time after concrescence of the neural cords, appear-
ing in cross-sections of the ganglionic regions as a clear punc-
tate, bilobed mass on the dorsal side just beneath the mesoblas-
tic sheath, which is still very thin. On tracing the sections
forwards the bilobed fibrillar mass grows steadily larger, and
may be seen to be separated into two distinct bundles in the
commissural regions, the interval between the two bundles being
occupied by a triangular mass of cells that extends upward
from the nerve-cells on the ventral side and comes into contact
above with the dorsal mesoblastic investment.

The neurochord first distinctly appears in the ganglionic
regions in the upper part of the fibrillar mass, and in its earliest
distinguishable condition already shows the three fibres charac-
teristic of the adult. Its precise origin is difficult to determine.
In the ganglionic region it unquestionably lies in the fibrillar
mass, and may often be seen to be separated by a distinct line
from the mesoblastic investment. In the commissural region it
becomes lost in the apex of the mass of cells that separates the
two halves of the fibrillar mass. All my preparations indicate
that the giant-fibres arise by direct differentiation from the
dorsal portion of the fibrillar mass, and not from the mesoblastic
investment, —a conclusion which is entirely opposed to Vejdov-
sky’s apparently clear and careful account (No. 44, p. 93).
There can be little doubt, however, from recent anatomical
studies (see Nos. 17, 37, 42) of the essential correctness of the
original view of Leydig and Claparéde, according to which the
colossal fibres of the neurochord are specially modified nerve-
fibres, which have probably assumed a supporting function.

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 419

X. ExcrETORY ORGANS.

The following account of the development of the nephridia
will be facilitated by a short review of our present knowledge
of the subject. For the sake of brevity I shall pass over most
of the earlier literature and consider only the results of more
recent studies. (For fuller reviews of the literature, see Vejdov-
sky, No. 44; Bergh, No. 8; Eisig, No. 16; and Meyer, No. 35.)
The development of the nephridia in the Polychaeta has been
most carefully studied by Meyer, to whose interesting work
reference will be made further on. Our present knowledge of
the nephridia in the Oligocheta rests in the main upon the
beautiful researches of Vejdovsky, whose great work on the
Oligochzeta (No. 44) must long remain a standard work of refer.
ence for students of annelid morphology.

Vejdovsky has clearly demonstrated the fact, suspected by
Kleinenberg (No. 28) and definitely asserted by Bucinsky (No.
9), that the permanent nephridia in the Oligochzeta arise from
two sources, their inner portion being formed in the somatic
mesoblast, their outer portion (‘Endblase’’) arising as an ecto-
blastic invagination. According to these authors the ectoblas-
tic portion comprises only the so-called muscular part of the
nephridium, while the glandular and ciliated portions, with the
peritoneal funnel, are formed from the mesoblast.

Vejdovsky has shown, moreover (No. 46), that in the course of
the embryonic development of Oligocheta (Rhynchelmis, Lum-
brictd@), no less than three sets of excretory organs are formed,
apparently quite independently of one another. The first of
these are the well-known “ Schluckzellen,” a short account of
which has been given at p. gor. By Hatschek they were sup-
posed to be concerned in the ingestion of albumen by the young
embryo. Vejdovsky has, however, shown them to be connected
with a system of delicate ciliated canals which lie in the space
between the ectoblast and entoblast, and communicate with the
outside through pores in the Schluckzellen ; the latter structures
are therefore undoubtedly to be regarded as larval organs of
excretion. They wholly disappear in later stages.

The “larval excretory organs”’ are succeeded by indepen-
dently developed “provisional” or “embryonal” organs (pro-
nephridia) which are almost certainly homologous with the

420 WILSON. [Vot. III.

“head-kidney”’ (Kopfniere) of Polygordius, Echiurus, and many
Polycheta. These organs are in the form of a pair of straight
ciliated canals situated in the anterior part of the body, above
or at the sides of the alimentary canal, and extending into the
head-cavity. The canals are closed internally, but open to the
outside, according to Vejdovsky, at their anterior ends near the
sides of the stomodzeum ; but according to the later studies of
Bergh on Criodrilus (No. 8) the external opening is at the
posterior end of the organ near the median line on the dorsal
side of the body.

The provisional nephridia ultimately degenerate and are fin-
ally succeeded by the permanent nephridia of the trunk-region.
Each of these arises (in Rhynchelmts) according to Vejdovsky,
from a single mesoblastic cell situated on the posterior face of a
dissepiment which multiplies to form a straight solid cell-cord,
ending in front in a large cell from which the funnel is ulti-
mately derived, and which soon acquires a closed lumen contain-
ing a single actively vibratile flagellum. (The flagellum does not
appear in the Lumbricidz.) This stage, which is designated as
the pronephridium, is regarded by Vejdovsky as homodynamous
with the head-kidney. The cilium-cell (“‘pronephrostome’’) of
the pronephridium gives rise to the funnel of the adult, the
glandular portion grows out as a loop-shaped lateral appendage
from the body of the pronephridium, and the end-vesicle or
muscular part is formed as an invagination from the ectoblast,
which is connected with the glandular part by the persistent
body of the pronephridium (No. 46, p. 683; No. 47, pp. 699,
700 for figures).

Bergh (No. 8) gives an account of the development of the
nephridia in Crzodrilus, which agrees, broadly speaking, with
that of Vejdovsky, but differs in the important particular that
the entire nephridium, zxcluding the end-vesicle, is described as
arising from the somatic mesoblast. i

Let us now turn to the results of Meyer in respect to the
Polychzeta (Nos. 35, 36), considering first his earlier studies,
which were based for the most part on the study of Polymnia
nebulosa. Meyer did not directly observe the origin of the
end-vesicle (Endcanal), but gives reasons for his belief that it is
invaginated from the ectoblast (Zc. p. 664). The most im-
portant result of his work is, however, that the funnel arises quite

No. 3.] ZHE EMBRYOLOGY OF THE EARTHWORM. 421

separately from the glandular part of the nephridium. To quote
his own words (fc. p. 654): ‘Alle bleibenden Nephridien
entstehen zu einer Zeit, wenn das Peritoneum in der bereits
segmentirten Larve im Allgemeinen schon den histologischen
Charakter angenommen hat, den es bei den erwachsenen Thieren
besitzt. Aus faltenartigen Erhebungen desselben, welche sich
gegen die gesonderte Anlage des Nephridialschlauches hin
nach hinten ausstiilpen, mit den letzteren in Verbindung treten
und sich mit einem inneren Wimperbesatz bekleiden, gehen die
Trichter hervor; die Schlauche dagegen bilden sich aus retro-
peritonealen, anfangs soliden Zellstrangen, die nach ihrer Verei-
nigung mit den Nephrostomen einen flimmerden, terminal nach
aussen durchbrechenden Achsencanal erhalten und zu zweischen-
keligen Schleifen auswachsen.” At page 663 he expresses the
opinion that “die Nephridialschlauche einem retroperitonealen
Gewebe entstammen und somit von den Peritonealtrichtern
morphologisch verschieden seien,” and adds that a similar mode
of development is characteristic of the development of Psygmo-
branchus. Meyer does not commit himself to any definite state-
ment as to the origin of the retroperitoneal cells, but promises
to discuss this question in a future work.

In his second paper (No. 36, pp. 463-476) Meyer describes in
detail the development of the nephridia in Psygmobranchus.
The funnel is here shown to be derived from the anterior
(mesoblastic) wall of the dissepiment (p. 472), while the glan-
dular part arises from a single “retroperitoneal” cell which is
at first wholly separate from the funnel and only secondarily
comes into connection with it (p. 468). The origin of the
retroperitoneal cells still remains however in doubt.

In 1886 (No. 51) Whitman announced the important dis-
covery that the nephridia arise in C/epszne from a longitudinal
cell-cord on each side of the body, which lies between the
ectoblast and entoblast and forms part of the middle stratum
of the germ-bands described by Metschnikoff many years before
(No. 34). These cell-cords are derived from two large cells
(nephroblasts) on each side the body, which arise from the same
basis as the neuroblasts.

In 1887 I showed (No. 54) that in Lambricus the nephridia
likewise arise in connection with a longitudinal nephric cord
‘ that is obviously homologous with the corresponding structure

422 WILSON. [Vot. III.

in Clepsine, and is likewise formed by the proliferation of a pair
of teloblasts that arise directly from the ectoblast. I asserted
in this paper (which was written before I had seen the works
of Vejdovsky and Meyer) that the funnel arose in the peri-
toneal mesoblast, independently of the glandular tube which was
formed as an outgrowth from the nephric cord and must there-
fore be of ectoblastic origin.

From the foregoing review it appears that there is still a very
wide divergence of opinion in respect to the origin of the nephridia,
Bergh representing one extreme (which agrees with the earlier
accounts of Kowalevsky and Hatschek) according to which the
the entire nephridium (in Crtodrilus ) is mesoblastic; Whitman,
representing the opposite extreme, asserting the origin of the
entire organ from the ectoblast ; while Vejdovsky and Meyer
agree in asserting the double origin of the nephridia; though
they differ in some very important details. I pass now to a
description of my own observations on Lumobricus.

I have not specially studied the larval organs or “Schluck-
zellen,’ and can give no additional facts in respect to their
structure and mode of origin. As stated at p. 402, I have failed
to find them in Z. fetidus, though they are easily demonstrable
in ZL. communis and in L terrestris. It seems not improbable
that their absence in ZL. o/¢dus may be correlated with the pres-
ence of the peculiar glandular (?) thickening of the ventral lip
of the stomodzeum described at p. 413; but I have failed to find
the slightest indication of any excretory function in this struc-
ture. In the other two species the remains of the “ Schluck-
zellen”’ can be observed up toa comparatively late period (e.g. in
the stages shown in Figs. 79, 80), though much diminished in
size, lying as a granular mass between the entoblast and ecto-
blast a considerable distance behind the cephalic cavity in the
median dorsal line.

As regards the “ provisional” excretory organs, or head-kid-
neys, my observations are very unsatisfactory. They can be
clearly observed in living embryos of ZL. communis at about the
stage of Fig. 48 as a pair of very delicate longtitudinal tubes
lying apparently on the dorso-lateral wall of the archenteron,
extending forward at the sides of the stomodzeum and lined by
actively vibratile cilia. In section (Fig. 92) they appear to be
actually embedded in the wall of the archenteron, whence they

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 423

may be traced forwards into the head-cavity, and backward to a
point near the dorsal median line; here they pass into the ecto-
blast, but I have not found any communication either with the
exterior or with the head-cavity. The important problem of the
relation of these organs to the permanent nephridia I have en-
tirely failed to solve ; this question can be studied to far better
advantage in forms like Crtodrilus, where the head-kidney is
much larger.

We may now turn to the permanent nephridia. I have stated
(p. 390) that these organs arise in connection with a contin-
uous cell-cord of ectoblastic origin that forms part of the middle
stratum of the germ-bands and lies alongside of the neural cord
(Figs. 49, 59, 63, 72, etc.). Each nephric cord terminates be-
hind in a pair of teloblasts derived from the ectoblast. The
entire nephric cord is formed by the continued divisions of these
“nephroblasts,” which agree precisely with the neuroblasts in
structure, action, and mode of origin. In early stages each
nephric cord consists behind of a double row of cells, each row
terminating in one of the nephroblasts. Passing forwards the
rows are no longer separated by any definable limit, and the
nephric cord consists of an irregular series of cells which
passes upwards beside the neural row and is lost at the sides of
the stomodzum ; beyond this point I have never been able to
trace it, either in sections or in surface-views. The general re-
lations of the nephroblasts and the nephric cords to the remain-
ing elements of the germ-bands are at first precisely similar to
those of the neuroblasts and the neural cords, as may be seen in
Figs. 53, 54, 71, 72, 90, 91. At first they lie at the surface of
the body and form part of the general ectoblast; afterwards
they sink beneath it so as to lie between the outer ectoblast and
the mesoblast. The nephric cells closely resemble those of the
general ectoblast and of the neural rows, but as a rule stain
more deeply than the neural cells and less deeply than those of
the ectoblast, so that all these structures appear with remarkable
distinctness in cross-sections, double-stained with borax-carmine
and Kleinenberg’s hzematoxylin.

In surface views of carefully stained germ-bands spread out
in glycerine (Fig. 63) the nephric rudiments are clearly seen to
lie along the line of the nephric cords. In both cross and longi-
tudinal sections they may be traced directly into connection

424 WILSON. [Vot. III.
with these cords. In the short preliminary paper already
referred to I stated that the entire nephridium, excepting the
funnel, was derived as an outgrowth from the nephric cord, and
was therefore of ectoblastic origin—a result in accordance
(except as regards the funnel) with Whitman’s conclusions in
respect to C/epsine, though this author did not follow the
development far enough to determine the origin of the inner-
most portion of the organ. This statement was based upon the
following facts, all of which have been repeatedly verified in a
number of species of Lumbricus, and are illustrated by Figs. 83-
88, Pl. XXI. The funnel arises by the division of a large
cell (f), which is differentiated at an early stage just at the
anterior angle between the dissepiment and the somatic mesoblast
(Figs. 83, 84), and manifestly arises from the mesoblast. Below
and behind this cell a group of cells is formed out of which arises
the body of the nephridium (zp.). In all its stages this group
of cells can be traced directly into continuity with the cells of
the nephric cord. The cells are disc-shaped and are arranged in
a single row which ultimately becomes perforated through its
centre to form the excretory canal. Almost from the very start
these cells can be clearly distinguished from an investing layer
of more or less flattened mesoblastic cells which are contin-
uous with those forming the dissepiments and ultimately give
rise to the peritoneal investment of the nephridium (Figs. 83,
85, 88).

In longitudinal sections the nephric cords present posteriorly
exactly the same appearance as the neural cords and are sep-
arated by a perfectly clear line from the mesoblast. Passing
forward, however, this line fades away in the region of the
youngest nephridia, so that it becomes extremely difficult to
determine the relation of the nephric cord to the mesoblast.
In this region the whole body-wall appears considerably thick-
ened, and the only parts of the nephridia that can be positively
identified, are the funnel-cells which form a regular series and
are easily recognizable by their enormous nuclei. A little further
forward, however, the relations can clearly be made out, and the
cells are seen to be arranged in the manner already described.
Whatever be its significance, there cannot be the slightest
doubt that the nephridia, in their earliest recognizable form are
connected in the manner described with the nephric cord,

No. 3.| ZHE EMBRYOLOGY OF THE EARTHWORM. 425

though, owing to the fact that the nephric cords are somewhat
wider than the nephridia themselves, this connection will not be
seen, unless the section pass precisely through the right point,
as shown for example in Fig. 86. To this fact is due, as I
believe, Bergh’s failure to observe the connection of the nephric
rudiments with the ectoblast. I shall not undertake to explain
this author’s very positive statement (which is made the text of
an extravagant critique of my own work), that the ectoblast is
one-layered outside the nephric rudiments, until I have had
an opportunity to examine for myself the development of these
organs in Cyviodrilus, a subject which apparently needs re-inves-
tigation.

The appearances I have described irresistibly suggest the
interpretation given in my former paper, viz.: that the funnel
and the investing cells alone are mesoblastic in origin, the body
of the nephridium being derived as an outgrowth from the
nephric cord. This conclusion is supported by Whitman’s
observations on C/epsine, where the peculiar granulation of the
nephric cells and their behavior with certain reagents renders
the development of the parts even clearer than in Lamoricus.
It fits in, moreover, completely with Meyer’s observations on the
Polychzeta, as far as they go. The “retroperitoreal’”’ tissue of
this author (which he is careful to distinguish from the perito-
neal mesoblast) corresponds exactly with the tissue from which
the nephric rudiments arise, having the same relations to the
investing cells and to the funnel. Unfortunately he has not
yet determined its origin, and until this all-important question
is answered, the nature of the glandular part of the nephridium
cannot be established. It is, however, interesting to note that
in Psygmobranchus, as in Lumbricus, the nephric foundations
alternate regularly with those of the setigerous glands (cf: No.
36, Taf. 23, Fig. 2), apparently forming with them a continuous
series, and it seems hardly too much to venture the prediction
that they will be found to have a like origin.

As regards the origin of the glandular portion of the nephrid-
ium in Lumbricus: from the numerous preparations in my
possession, I should still have no hesitation in positively reas-
serting my original statement as to its ectoblastic origin, were
it not for Vejdovsky’s careful observations on other Oligocheta,
which seem to be opposed to such a conclusion. In view of

426 WILSON. [VoL. III.

these observations I cannot deny the possibility that the glan-
dular part may be differentiated from the somatic mesoblast at
a very early period, fusing immediately with the cells of the
nephric cord, which may give rise only to the end-vesicle. Until,
however, the relations of the nephridia to the nephric cords
(which have escaped the attention of all other observers of the
Oligochzta) have been made clear in other forms, the question
must remain open, for I do not believe it is possible to attain
an absolutely certain result by the study of Lusbricus alone.

Whatever be the result, there can be no doubt in the case
of Lumbricus of the intimate connection of the nephridia with
ectoblastic nephric cell-cords and their partial derivation from
them. The comparison of the nephric cord with the vertebrate
segmental duct, which I drew in my earlier paper, has been
criticised by Eisig, in an appendix to his monograph of the
Capitellidz, on several grounds. I may, however, point out
that it differs but slightly from his own views, according to
which the vertebrate segmental duct is to be regarded as the
posterior extension of the ectoblastic part of an anterior nephrid-
ium, and that: it gives a datum hitherto lacking to the com-
parison, by showing in the annelids a continuous differentiated
ectoblastic structure connecting the anterior nephridia with
those lying behind. As to Eisig’s criticism of my comparison
of the nephridia of annelids with the pronephros of Vertebrates,
I fully acknowledge its force.

The nephridia rapidly elongate, and, owing to the fact that
their ends are fixed, bend into a U-shape with the loop directed
dorsally and laterally. Meanwhile the central cord of cells
becomes perforated from end to end by a delicate canal which
becomes ciliated ; the funnel-cell divides into a group of ciliated
cells situated on the anterior face of the dissepiment which
form the funnel, and the organ becomes fully functional long
before the young worm is hatched. I have not attempted to
follow in detail the histological differentiation.

The Sete.— The setigerous glands of the inner or ventral
series arise opposite the nephric cord in regular alternation with
the nephridia, and transverse and longitudinal sections clearly
demonstrate the fact that they take their origin in the nephric
cords. In Fig. 86 the outer end of the nephric rudiment
appears to turn upwards and backwards so as to adjoin the fun-

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 427

nel of the succeeding nephridium. In favorable longitudinal
sections this appearance may be followed from somite to somite,
so that the series of nephridia appears to form a continuous
cell-cord thrown into S-shaped undulations. On following the
series forward, the group of cells marked s.g/. in Fig. 86, which
lies between two succeeding nephridia, becomes enlarged, pro-
jects into the coelomic cavity, is surrounded by a mesoblastic
investment, and a seta is developed in its interior (Figs. 85 to
88, and Fig. 93). The first setais soon followed by a second, and
the two soon force their way through to the outside. The mes-
oblastic investment persists and gives rise to the muscles of the
sete. The setigerous glands of the inner series therefore
grow forth from the nephric cords in regular alternation with
the nephridia, and are accordingly of ectoblastic origin, being
derived from the middle stratum of the germ-bands.

The outer setigerous glands arise from the middle stratum of
the germ-bands, lateral to the nephric cords, as solid ectoblastic
invaginations invested by mesoblast precisely like those of the
inner series. There can be little doubt that they arise from the
lateral cell-cord where this is present, though I have been unable
to demonstrate this, owing to the early disappearance of the
line of demarcation between the lateral and nephric cell-cords.

Several interesting questions suggested by these facts may be
briefly pointed out at this point. If, as I suspect, the lateral
teloblast be in reality a setiblast, an interesting side-light is
thrown on the affinities of the Hirudinea, for the lateral teloblast
of Clepsine is certainly homologous with that of Lusmdbricus, and
its existence would seem to indicate the former possession of
setae by these animals. It is an interesting fact, secondly, that
the nephric cord is double, while the lateral cord is single, and
it is not impossible that one of the so-called nephroblasts may
in reality be a setiblast like the outer teloblast, though it is not
possible to distinguish certainly the setigerous from the nephric
elements of the so-called nephric cord until a comparatively late
stage. In any case the origin of the setigerous glands, while
showing a very remarkable and interesting specialized develop-
ment, is entirely in accordance with the results of Kleinenberg,
Vejdovsky and others as to their ectoblastic origin.

428 WILSON. [Vor. III.

PART IIl.

GENERAL QUESTIONS.

There is reason to believe that Lumbricus is a somewhat
specialized form, both anatomically and embryologically, and it
is therefore necessary to be cautious in drawing general con-
clusions from the phenomena of development, especially in
respect to their phylogenetic significance. Yet the very fact
of secondary modification having taken place gives value to a
comparison of the development of Lwmdricus with that of other
annelids, since it gives in some degree a test of the weight that
can justly be assigned to the various features of the ontogeny.

I may recall the well-known fact that among the annelids, as
among many other animals, two types of development occur,
which Balfour has conveniently designated as the /arva/ and the
fatal types. The former, represented typically by the develop-
ment of Polygordius, Eupomatus, etc., is indirect, and is charac-
terized by the appearance of a free-swimming Trochosphere
stage, in which the trunk is more or less completely suppressed
and the head-region is highly developed. The second or fcetal
type occurs in forms like Lumbricus, Criodrilus, Clepsine, etc.,
which undergo a direct development within an egg-capsule, sur-
rounded by nutritive albumen. In this type the development is
abbreviated, the free-swimming stage is more or less completely
suppressed, and the trunk-region is early developed. [Hatschek
has pointed out that the foetal forms may be arranged under
two divisions, one including those like Lesmbricus, which have
little deutoplasm in the ovum and develop by embolic invagina-
tion ; the other comprising such forms as Evaxes or Clepsine, in
which the ovum is heavily laden with deutoplasm and the gas-
trulation is consequently of the epibolic type. ]

It is furthermore generally agreed that both the larval and
foetal forms have undergone more or less extensive secondary
modification, the former through adaptation to the conditions of
free-swimming larval life, the latter through simplification and
abbreviation caused by the lack of those conditions, and perhaps
by special adaptations caused by the peculiar mode of nutrition.
In view of these facts it seems clear that agreement in any
feature of development between the larval and foetal types may

No. 3.] ZHE EMBRYOLOGY OF THE EARTHWORM. 429

be taken to indicate with considerable probability the primitive
character of such a feature, and that, conversely, those features
in which the two types differ are due to secondary modification
having taken place in one or both forms. Obvious as this prin-
ciple appears, its importance seems to me not to have been
sufficiently recognized in a number of recent papers on the sub-
ject, and it must carefully be kept in view in the following dis-
cussion.

XI. RELATIONS oF THE HEAD! (Prostomium) AND TRUNK.

The most fundamental question of annelidan morphology con-
cerns the relation between the head and the trunk. Indeed, it
is not too much to say that this question, involving as it does
the interpretation of the Trochosphere, of the teloblasts, and of
metameric segmentation, is one of the most important problems
of comparative morphology, though it is admitted by a number
of leading morphologists to be incapable at present of more
than a conjectural solution. The limits of this paper do not
permit a review of the very extensive literature on the subject,
and I shall therefore refer at this point to only two of the latest
papers. Fraipont has given in his monograph of Polygordius
(No. 15) an admirable review of recent discussions of the Tro-
chosphere, to which Whitman (No. 52) has added an important
discussion of the teloblasts and of growth by concrescence, —
questions which were not specially considered by Fraipont.
Both these authors admit that the Trochosphere larva of anne-
lids still remains (to use Whitman’s phrase) a morphological
puzzle, which can only be solved by further extended investiga-
tion —an admission which is fully justified by the diametrical
opposition of the views of leading authorities on the subject.
It would therefore be profitless to enter upon an exhaustive dis-
cussion, and I wish only to make a few suggestions in regard to
certain points which do not seem to me to have been sufficiently
considered and on which a certain amount of light is thrown by
the development of Lambricus. They must, however, be intro-
duced by a short review of the general question.

1] shall use the word “ head” to designate that part of the body (often called pro-
stomium, prz-oral lobe, or cephalic lobe) that contains the anterior median unpaired
cavity that lies in front of the first dissepiment, and obviously represents the principal
cavity of the Trochosphere.

430 WILSON. [Vot. III.

Either the Trochosphere larva of annelids is the larval repre-
sentative of an ancestral non-metameric form, as held by Hat-
schek, Kleinenberg, and Whitman, or it is a purely secondary
form as held by Lang and Sedgwick. Under the former view the
head must be regarded as phylogenetically the oldest part of
the animal, and the trunk as a neomorph, the origin of which
involved the origin of metamerism. According to the second
view, head and trunk are but secondarily differentiated parts of
the ancestral body, and the retardation or rudimentary condition
of the metameric trunk-region that now characterizes the Trocho-
sphere is due to cenogenetic changes ; thus the origin of meta-
merism may have been antecedent to the appearance of the
Trochosphere, and the head not phylogenetically older than
the trunk.

There is no means of deciding between these two conflicting
views save by a thorough investigation of the actual anatomical
and embryological relations between the head and trunk—a
question which I shall now briefly review.

The head has been asserted to differ morphologically from
the trunk in the following principal characters : (1) in containing
no reproductive organs ; (2) in arising from a pair of mesoblastic
foundations that arise independently of the trunk mesoblast ;
(3) in containing an unpaired cavity (“primary body-cavity”’)
which is the remains of the blastoccel traversed by mesenchy-
matous cells, and not homodynamous with the coelomic cavities
of the trunk (“secondary body-cavity”’), since these arise by
cleavage of the mesoblast and are surrounded by mesothelial
walls; (4) in possessing a nervous system (Scheitelplatte, of
Hatschek, or apical neural plate) which is primitively unpaired
(Hatschek), and arises independently of the ventral chain (Klein-
enberg, Salensky, etc.).

Let us examine these statements. The first may be set
aside, since many of the trunk somites are sterile like the head.
The second has been disproved so far as the Che@topods are
concerned, by Hatschek, who has clearly shown that the head-
mesoblast arises by the forward growth and union of the two
mesoblastic trunk-bands, a conclusion which Kleinenberg like-
wise reached in his later studies (Lopadorhynchus), and with
which my own observations entirely agree.

The third statement is true as far as the unpaired character

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 431

of the head-cavity is concerned, but the other points are of
secondary importance. In Polygordius and the other larval
types the head-cavity is manifestly derived from the blastoccel
and is always unpaired. My observations on Lumbricus leave
no doubt that the head-cavity is median and unpaired in the
foetal types also, and except for its very small size has precisely
the same morphological character as in the larval types. [This
result is entirely opposed to the observations of Kleinenberg, —
which have been especially emphasized by Balfour, — according
to. which the head-cavity in Lusmbricus arises by the fusion of
a pair of lateral cavities apparently homodynamous with ¢ruzk-
cavities.| “The mesenchymatous character of the cephalic mes-
oblast is obviously of secondary importance; for it has been
shown that its cells not only have a common origin with those
of the trunk-mesoblast, but also extend throughout the trunk-
region (migratory mesoblast). Kleinenberg has shown, moreover,
that in Lopadorhynchus and some other Polychzta the splanchnic
mesoblast is formed by a process essentially identical with the
formation of the cephalic mesoblast, — z.c. by migration of the
cells through the blastoccel and their secondary arrangement in
a continuous layer,—and he has thus also proved that the
relations of the cephalic cavity to the blastoccel afford no ground
for Hatschek’s distinction between primary and secondary body-
cavity. I may add that the same conclusion is reached by the
study of the foetal types (though on a very different basis from
that adduced by Kleinenberg), for in these forms the blastoccel
completely disappears, and the head-cavity is a new formation.
In the larval types the coincidence of the head-cavity with the
blastoccel is an incidental result of the circumstance that the
blastocoel is large and persistent while the cephalic mesoblast
is of late origin and is never sufficiently developed to fill the
space between ectoblast and entoblast. This coincidence has
no more significance than the coincidence of the blastoccel with
the archenteric cavity which occurs among certain Amphibia.!
The fourth statement requires careful consideration. As far
as Lumbricus is concerned, it is untrue in both particulars ; for
the halves of the cephalic ganglion arise at the anterior ends of
neural rows, quite separate from each other, but in direct con-

1 See O. Schultze, No. 4o.

432 WILSON. [Vot. Ill.

tinuation with the foundations of the cesophageal commissures
and of the ventral chain. As regards the first point, Kleinen-
berg’s failure to observe the double foundation of the cephalic
ganglia seems to have been due simply to his not having studied
sufficiently early stages; for the earliest stage he figures is
already as far advanced as that shown in Fig. 79 of this paper,
in which the two ganglia have already fused.

On anatomical grounds there is considerable reason to believe
that the cephalic ganglionic mass was primitively unpaired, as
it still remains in Protodyri/us, and that its bilobed character in
the higher forms is the result of the bilateral differentiation of
the head (paired sense-organs, etc.). Hatschek endeavored to
show that a median unpaired foundation (Scheitelplatte) for the
cephalic ganglion was characteristic of annelidan development
generally (as typically shown in the development of Polygordius),
and that this apical plate represented the central nervous system
of the ancestral Trochozodn. A comparison of the actual
development of the various forms, however, not only shows a
marked divergence between the foetal and larval types, which
might have been expected, but also indicates that both types
must be more carefully examined before any trustworthy conclu-
sion can be reached in regard to the apical plate. As regards the
foetal types the evidence is conflicting, but on the whole appears
at present to indicate a double foundation for the cephalic
ganglia. The facts in Lumbricus seem to admit of no doubt,
and agree with Kennel’s observations on Ctenodrilus (No. 26) —
a form which possesses a very primitive nervous system. In the
case of Criodrilus, as Bergh has pointed out (No. 5), Hatschek’s
earliest figures (No. 18) show the apical plate as a distinctly
bilobed structure, though he describes it in the text as median
and unpaired. Vejdovsky positively asserts the unpaired char-
acter of the apical plate in Rhynchelmis (No. 44); but, as he
expressly states, he did not observe the apical plate until it had
become a large mass, entirely filling the cephalic cavity, and we
have seen that in Lwsmbricus the double character of the founda-
tion is only manifest at a much earlier period.

As regards the larval types, all observers agree that the
foundation of the cephalic ganglia arises in connection with an
unpaired sense-organ (“ Sinnesplatte’’), which is usually median,
but sometimes asymmetrical (Kleinenberg, Salensky). The

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 433

apical plate (Scheitelplatte) is primitively the central organ of
this sense-organ, and most observers agree that it is likewise
median and unpaired. Kleinenberg’s remarkable studies on
Lopadorhynchus and certain Phyllodoctde demonstrate, however,
that in these forms the nerve-cells connected with the apical
sense-organ form only a comparatively small part of the cephalic
ganglia, the greater part being formed from several completely
separate paired foundations. Kleinenberg’s observations, more-
over, afford considerable ground for regarding the apical plate
itself as having been primitively a paired organ; for in Lopa-
dorhynchus it lies from the first on the right side, and in the
corresponding position on the left side is a group of cells that
soon disappears, and is suspected by Kleinenberg to represent a
degenerate left apical plate. No other observer has studied the
origin of the cephalic ganglia in the larval types with any
approach to the thoroughness and care that characterizes
Kleinenberg’s work, and until a more adequate study of the
apical plate has been made in other larval types, its morpho-
logical significance must remain in doubt. On the whole,
therefore, it appears that no trustworthy basis for any funda-
mental morphological distinction between head and trunk can
at present be found in the mode of development of the cephalic
ganglia. The adult cephalic ganglia in higher annelids certainly
are paired, and it would seem that their mode of origin (whether
from a paired or unpaired foundation) depends simply on the
time at which the bridge of neural tissue between the two halves
is formed, and this time is shown by the facts to be variable.
As regards the second point, Kleinenberg lays great stress
on the supposed independent origin of the cephalic and trunk
ganglia, which he interprets (in accordance with the theory of
development by substitution), as follows: The ring-nerve of the
prototroch represents the ancestral central organ, and is the
homologue of the ring-nerve of a medusa. In connection with
it, in the course of the ancestral development, arose separately
the cephalic ganglia in front (umbrellar region) and the ventral
trunk-chain behind (sub-umbrellar region), the ring-nerve at first
forming the connecting link between them, but subsequent!y
disappearing in the adult and appearing only in the larva
(Trochosphere). In the foetal types the ring-nerve has dis-
appeared even from the larval stages, and the cephalic ganglia

434 WILSON. [Vo. III.

and the ventral chain are, therefore, at first not connected with
each other.

This explanation is extremely ingenious, but I must point out
the fact that the separate origin of the cephalic ganglia and the
ventral chains in the foetal types is by no means an established
fact, and that, even if it were, it would be capable of a much
simpler interpretation. Hatschek has always maintained the di-
rect and primary connection of the apical plate with the ventral
nerve-chain, and this view is supported by Vejdovsky’s observa-
tions on Rhyuchelmts and my own on Lumbricus. In Lumbricus
the cephalic foundations are from the first in continuity with
those of the ventral chain, though the cesophageal commissures
are represented only by rows of neural cells, which are still fused
with the general ectoblast, and would scarcely be recognizable
were it not for their connection with the neuroblasts. In later
stages the commissures lag somewhat behind the other parts,
and may thus easily be overlooked. It appears, therefore, as
Hatschek has pointed out (No. 20, p. 72), that the entire ques-
tion as to the separate or common origin of the cephalic and
trunk ganglia relates simply to the period at which the ceso-
phageal commissures are differentiated; and the possibility of
secondary acceleration or retardation in these structures cer-
tainly cannot be denied in view of the fact that in many other
metameric animals, entire somites in the middle region may lag
far behind other parts, or even be suppressed for a long time —
as for instance in the Decapod zoéa.

To sum up, it appears from the foregoing discussion that the
only certain embryological ground for maintaining the contrast
between the head and trunk lies in the fact that the head-cavity
is unpaired, while the trunk-cavities are paired; and this I
believe to be a real, though not a fundamental distinction. The
fact that the foetal and larval types agree in this respect indi-
cates its primitive character, and this conclusion is, moreover, so
strongly supported by the facts of comparative embryology that
no one would have called it in question but for Kleinenberg’s
account of its development in Lumobricus.

All the evidence seems to show, therefore, not only that the
cephalic cavity is unpaired, but that this is an ancestral feature
of the annelid body. But the evidence appears to me to indicate,
furthermore, that the head-cavity is to be regarded as homo-

No. 3.} ZTHE EMBRYOLOGY OF THE EARTHWORM. 435

dynamous, not with the double cavity of a single somite, but
with one of the patr of cavities, by the fusion of which each
celomic cavity of the trunk arises ; in other words, the coelomic
cavities, with their mesoblastic walls, can be most simply and
accurately conceived as forming an elongated ring, the two
halves of which lie at the sides of the alimentary canal, and are
connected in front by the head-cavity, the walls of which become
differentiated into the parts of head! Can this be regarded as
a characteristic of the ancestral body? If so, the retardation of
the jtrunk-region in the larval Trochosphere is obviously a
secondary feature of development, and the head cannot be
regarded as older than the trunk. Under this view, moreover,
it would follow that the concrescence of the mesoblastic and
neural bands that is so striking a feature of annelidan develop-
ment must be regarded as an ancestral feature, and not as the
result of secondary changes caused by special embryonic con-
ditions. This question I shall now briefly discuss.

XII. ConcrRESCENCE AND THE BLASTOPORE.

We are indebted to Whitman for a most interesting analysis
of the phenomena of concrescent growth in the annelid embryo,
the process being conceived as a secondary feature of develop-
ment, brought about by accumulation of deutoplasm in the
ovum. His general conclusions (in respect to C/epszne) are
stated in the following passage (No. 52, p. 175; the italics are
mine) :—

“Among the more important differences remaining to be
noticed are those which have been brought about under the
influence of the food-yolk. The process of gastrulation, the
form of the blastopore and its relations to the mouth, have been
very profoundly modified in this way. The trunk-bud of the
foetal Trochosphere has been carried far from its original post-
oral position; and, as the result of this displacement, we see
the halves (germ-bands) of the trunk (which develop side by side
as a unit in the larva) formed separately and carried over the

1] may point out the fact that the ccelom of annelids is generally agreed to be
primitively divided by dorsal and ventral mesenteries into right and left cavities,
though the dorsal mesentery often disappears; and that the discovery of the excretory
organs of the head has still further lessened the supposed contrast between head and
trunk.

436 WILSON. mm [Vere

massive sphere of yolk in such a manner as to meet along the
median ventral line. TZhzs whole process of ctrcumcrescence and
concrescence has arisen secondarily, in adaptation to fetal con-
ditions that do not exist in the larval form. The blastopore, if
we include the space traversed in the closure of the germ-bands,
has been stretched out of all proportion to its original dimen-
sions, so that it no longer represents the primitive Gastrula-
mouth, but merely a secondary prolongation of it backwards
along the whole ventral line of the body. In the embryonic
Trochosphere we find the blastopore already closed before the
trunk-bud begins to develop; hence the line of closure (‘ Gas-
trula-raphe”’) is limited to the ventral line of the Trochosphere.
As the metameric body-region is not yet developed, it is evident
that the posterior limit of the primitive blastopore falls within
the non-metameric region, from which the head-segment of the
adult animal is formed.”

Concrescence, as thus conceived, is, therefore (to use Professor
Whitman's own expression), a process of restoration, by which
the two halves of the embryo, which have been mechanically
separated by the backward extension of the blastopore along the
median ventral line, are brought together again. But a broader
examination of the question demonstrates the inadequacy of this
explanation, clear as it at first sight appears to be. It is per-
fectly obvious that the history of the mesoblastic and neural
elements in Lumbricus is essentially the same as in Clepsine and
other epibolic foetal types. In both the mesoblastic and neural
bands are at first widely separated throughout the middle region
of the trunk, and subsequently undergo a process of union along
the median ventral line. Lambricus differs only in the accelera-
tion of the ectoblastic part of the germ-bands, which outstrips
the other elements and thus closes in the blastopore while the
neural and mesoblastic elements still lie quite at the sides of
the embryo. Yet the embryo contains very little food-yolk ; the
gastrulation is of the embolic type, and hence the separation
and subsequent concrescence of the germ-bands cannot be
explained under Whitman’s view, unless we suppose the gas-
trulation to be a secondary derivative of an epibolic form.

In view of such a possibility, however, let us waive the case of
Lumbricus and consider the typical larval types. No one can
compare the history of the mesoblastic bands in C/epszne, in

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 437

Lumbricus, and in Polygordius, without perceiving that it is
essentially the same in all, though in Polygordius the ectoblast
extends over the ventral surface at an even earlier period than
in Lumbricus. In all, the mesoblastic bands lie at an early
period on opposite sides of the body throughout the trunk-
region, and their subsequent growth and union along the median
ventral line in Polygordius and the other larval types is closely
similar to the corresponding process in Lwmbricus, and scarcely
less striking than in the epibolic types. There is, however, no
food-yolk (Eupomatus, Hydroides), the gastrulation is of the
embolic type, the blastopore never actually extends between the
mesoblastic bands (since they are still undeveloped at the time
of its closure), and their wide separation must be due to some
other cause. The essential agreement in the history of the
mesoblastic bands between forms so different both in structure
and in the conditions of embryonic development as Clepsine,
Lumobricus, and Polygordius, is very strong evidence that meso-
blastic concrescence has some ancestral meaning, and was not
originally caused, though afterwards it was undoubtedly in many
cases modified and rendered more conspicuous, by accumulation
of food-yolk in the ovum.?

All of the evidence seems, therefore, to indicate that the
mesoblast (with the contained coelomic cavities) originally lay
in two masses that extend along the sides of the alimentary
canal and joined in front of the mouth and also at the posterior
extremity. Concrescence is the ontogenetic repetition of the

-process by which these originally separate masses extended

dorso-ventrally around the archenteron and fused in the middle
line, and the explanation of this process must, I believe, be
sought in the relation of the germ-bands to the blastopore.

The posterior limit of the ventral surface of the embryo ZLam-
bricus may be placed at the point of union of the two primary
mesoblasts, and the anterior limit at the mouth. The blastopore,
therefore, occupies at first nearly the whole ventral surface, its
anterior lip corresponding with the anterior lip of the mouth, its
posterior lip lying just anterior to the primary mosoblasts. In

1] am aware that I have used the word “concrescence”’ in a somewhat broader
sense than that employed by Professor Whitman. The word, however, cannot logi-
cally be restricted to such cases as those of C/efsime, and to make such an arbitrary
limitation would be simply to ignore the real problem to be solved.

438 WILSON. * (Vou. III.

Eupomatus the blastopore, though smaller, has the same position,
and in both forms it closes from behind forwards, the foremost
portion persisting as the mouth. The blastopore also has the
same position in the epibolic types (Clepsine, Euaxrcs, etc.),
though, as Whitman has shown, its mode of closure has been
modified through the enormous accumulation of food-yolk in the
entoblastic part.

A comparison of Figs. 35 to 44 will show that the mesoblastic
and neural elements of the germ-bands in Lumdricus may be
most clearly conceived as forming a longitudinal ring surround-
ing the region of this primitive blastopore, and that concres-
cence of the germ-bands takes place throughout the middle
region of this ring along the line of union of the lips of the
blastopore, though these relations are somewhat obscured by
the fact that their various elements do not develop at the same
rate and the neural ring remains incomplete. Thus the anterior
part of both the mesoblastic and neural rings is only completed
after the blastopore has narrowed to form the mouth, and the
extreme posterior part of the neural ring appears never to de-
velop.

This view of the relation of the germ-bands to the blastopore,
taken in connection with the arguments in favor of the primitive
character of concrescent growth, points unmistakably to that
hypothesis as to the ancestral history of the blastopore first sug-
gested, as far as I am aware, by Biitschli (No. 10), and afterwards
developed at length by Sedgwick in his well-known paper on the
origin of metameric segmentation (No. 41). In spite of the
strong opposition with which this hypothesis has been received
in some quarters, and in spite of the difficulties which it, in
common with every other theory, has to encounter, it neverthe-
less appears to me to be the only one that gives any approach to
an explanation of the phenomena in question. If we suppose
the annelid blastopore to have given rise originally to both
mouth and anus by closure in the middle region (as it still does
in Peripatus), and that this process represents approximately
the phylogenetic origin of mouth and anus from the ancestral
protostome, the explanation of mesoblastic and neural concres-
cence becomes obvious. The primitive mode of closure of the
blastopore itself has been modified,—probably through the need
of a very early establishment of the mouth, — so that the con-

Nows-] “2HE ZMBRYOLOGY OF THE BARTHWORM. 439

crescence of its lips outstrips that of the other elements of the
germ-bands, and the anus is retarded in development. Con-
crescence of the neural and mesoblastic elements, however,
still follows the original mode of development, the lateral parts
of both rings long remaining separate behind the point where
the germ-bands diverge. The long continuance of this diver-
gence of the germ-bands behind, which is a remarkable feature
in the development of many if not all annelids, seems to be due
to the retention in this region of the embryonic condition to
allow the continued growth and elongation of the body.

The most obvious objection to this view lies in the fact (first pointed out
by Hatschek, as far as I am aware) that the proctodzum arises outside the meso-
blastic ring (¢.e. apparently behind the primary mesoblasts) and, therefore,
not in the region of the blastopore. This objection is, however, by no means
a fatal one, either in respect to the relation between anus and blastopore or
to that between the anus and the mesoblastic ring. The first point has been
fully considered by Sedgwick in his general discussion, and the differences
between the foetal and larval types in this respect show that the development
of the anus has been greatly modified. The second point loses much of its
force from the facts, first, that the position of the primary mesoblasts is vari-
able (compare Crzodrzlus, in which the mesoblastic ring is not closed behind
and the primary mesoblasts are widely separated from each other, or Zupoma-
tus, in which the mesoblasts lie at one period on either side of the anus) ; and
second, that upon the breaking up of the primary mesoblasts, which takes place
in Lumbricus just before the invagination of the proctodeum, the mesoblastic
bands grow around the proctodzum and join in the middle line above it.
Hence it cannot be denied that the present position of the anus outside the
primary mesoblastic ring may be due to secondary changes having occurred
in the position, either of the anus, of the ring of mesoblast, or of both.

XIII. THe TRocHOSPHERE AND THE TELOBLASTS.

It is obvious that if the foregoing interpretation of the annelid
embryo be accepted, the Trochosphere cannot be regarded as a
primary larval form (representing an ancestral “ 7rochozoén”’),
but as one which has undergone very great secondary modifi-
cation through retardation of the trunk-region accompanied by
early and special differentiation of the head. That it is sucha
secondary form, appears to me to be practically demonstrated by
the teloblasts which are so marked a feature of the larva. Proba-
bly no one will maintain that these remarkable structures are
ancestral in the sense of having ever existed as functional adult
organs. Physiologically they are specially differentiated growth-

440 WILSON. [Vou. III.

centres, precisely analogous to the apical cells of plants, and
like them adapted to facilitate a rapid and continuous elongation
of the body in one direction. Morphologically they must be
taken to represent parts that have been retarded in development,
and at the same time extremely reduced and concentrated by a
precocious segregation of material. In other words, the telo-
blasts represent the rudimentary trunk of the Trochosphere, and
indicate the former presence in the larva of a developed trunk,
which is now temporarily reduced in favor of the head, the latter
having meanwhile acquired special larval organs of locomotion
and sensation. The evidence at our command appears to me
to indicate that the annelid Trochosphere is a secondary larval
form analogous in its mode of origin to the Crustacean Nauplius,
which was itself so long regarded as an ancestral form. It is
now generally admitted that the former conception of the Nau-
plius is no longer tenable,! and that the characteristic features
of the Nauplius are of purely secondary origin, a few anterior
somites having been accelerated and specially differentiated to
meet the requirements of larval existence, while the others have
been retarded or for the time being entirely suppressed. I can
see no valid reason against regarding the Trochosphere as hav-
ing arisen by an analogous process from an elongated segmented
ancestral form, the head-region or prostomium being enormously
developed and provided with special organs of sense and loco-
motion, and the trunk-region more or less retarded, becoming
reduced, it may be, to a mere trunk-bud, as in the typical larval
forms. It is no doubt an astonishing fact that the entire meso-
blastic trunk-region of an animal should have been compressed
into a single pair of cells, but it is scarcely more astonishing
than the complete secondary suppression of the long posterior
metameric trunk-region in the Nauplius.

It is instructive to notice that, as regards the retardation of
the trunk-region, a series exists among the annelids, which is,
broadly speaking, analogous to the series occurring among Crus-
tacean larve. Lumbricus stands midway between Polygordius
or Lupomatus on the one hand, and Euwaxes or Clepsine on the
other. In the latter the mesoblastic bands are fully established,
and join in front long before the epibolic gastrulation is com-

1 For reviews of this question, see Claus, No. 13, and Dohrn, No. 14.

No. 3.] ZHE EMBRYOLOGY OF THE EARTHWORM. 441

pleted. In Lumbricus the germ-bands are present in the gas-
trula, but are relatively much less developed than in Clepsine,
and they do not unite anteriorly until after the establishment of
the mouth. In Lupomatus, finally, the mesoblastic bands are
wholly rudimentary at the time the blastopore closes, but they
are nevertheless represented by the primary mesoblasts.

I am not prepared to discuss the case of Lofadorhynchus and
allied forms in which no teloblasts have been observed, for it is
very far from certain that they are not really present (see p. 443),
and their very general occurrence in the Trochosphere indicates
at present that they are to be regarded as characteristic of the
larva. :

To sum up: as:far as our knowledge goes, the development of
Lumbricus can be most simply and clearly interpreted in accord-
ance with Sedgwick’s hypothesis, as follows: (1) The ancestral
form possessed an elongated ventral blastopore that gave rise to
both mouth and anus by closure in the middle region ; (2) the
mesoblast and the nervous system originally formed a ring
around this blastopore, subsequently undergoing concrescence
throughout its middle portion as the blastopore closed; (3) the
coelomic cavities were arranged in a continuous series in the
mesoblastic ring, each lateral cavity lying opposite a correspond-
ing cavity on the other side of the body, and a single anterior
cavity lying in front of the mouth and giving rise to the head-
cavity ; (4) the larval Trochosphere is secondarily derived from
such a form by retardation or temporary suppression of the
trunk-region and early and extensive differentiation of the head-
region.!

Further than this I shall venture no conjecture as to the
character of the adult ancestral form, except to state that the
views suggested are reconcilable with the derivation of annelids
either directly from Ccelenterata, or from Platyhelminths, in ac-
cordance with the views of Balfour and Sedgwick, or Lang.
The essential feature of all these views is the identification of
the principal or longitudinal axis of the body with one of the

1 The apparent non-extension of the blastopore into the trunk-region in the larval
Trochosphere is under this view owing simply to the rudimentary condition of the
trunk at the time the blastopore is formed. The early closure of the blastopore is
probably due to the advantage of the earliest possible establishment of the mouth in
the free-swimming larva, which must procure its own food.

442 - WILSON. (VoL. III.

transverse axes of the gastrula, and hence of the Ccelenterate
ancestral type, which the gastrula in some degree represents ;
and we owe to Balfour the fruitful suggestion that the nervous
system of the Bilateralia may have arisen directly by the elonga-
tion of the circum-oral ring of the ancestral form. Kleinenberg
has shown in the clearest manner that this view is untenable, if,
as Balfour supposed, and Kleinenberg himself believes, the Tro-
chosphere is an ancestral form; for the adult nervous system
does not arise from the ring-nerve of the larva, and lies at right
angles to it. This objection, however, rests wholly on the sup-
posed homology of the Trochosphere ring-nerve with the circum-
oral ring-nerve of a medusoid form; and this homology, to say
the least, remains to be proven. On the other hand, the adult
nervous system, like the larval “ring-nerve,” certainly surrounds
the region of the blastopore, as I have endeavored to show ; and
if there is any force in the foregoing argument, the larval ‘“‘ring-
nerve” is essentially a secondary system, developed in connec-
tion with a purely larval locomotor organ. The possibility of
such an origin is rendered apparent by the fact that Polygordius,
and presumably other larval types as well (see Fraipont, No. 15),
has not one but several (in Polygordius six) parallel ganglion-
ated nerve-rings, of which only two supply the locomotor organ,
while the others form part of the general umbrellar nervous
system}

Grant that the ring-nerve of the Trochosphere is essentially
a secondary larval structure, and the objections to Balfour's
fundamental conception disappear, though some of the details
of his hypothesis must be modified.

XIV. MESOBLAST AND C@Lom.

Our knowledge of the mesoblast in annelids appears at pres-
ent to be in a very confused and unsatisfactory condition. In
all the foetal types (Oligochzeta, Hirudinea), and in many of the

1 Fraipont (/c., p. 56) is inclined to regard the fifth nerve-ring of Polygordius
(which supplies the prae-oral ciliated band, and which alone is provided with
ganglion-cells throughout its entire course) as the representative of the ring-nerve
of Lopadorhynchus and similar forms. Whether this view be well founded or
not, the prototrochal nervous apparatus of Polygordius differs remarkably from
that of Lopadorhynchus, etc., both in position and in structure.

No. 3.] ZHE EMBRYOLOGY OF THE EARTHWORM. 443

larval types (Polygordius, Eupomatus, etc.), the entire mesoblast
arises from a single pair of cells (teloblasts), which appear near
the time of gastrulation in the region of the posterior lip of the
blastopore, though they may be differentiated before the gas-
trula stage is reached, as in the foetal types generally. In a
number of the larval types, however (Lopadorhynchus, Alciope,
Asterope, Nauphanta, t. Kleinenberg; Pileolaria, Aricia, t. Sa-
lensky), it is asserted that there are no teloblasts, and that the
mesoblast is split off from the ventral ectoblast, long after the
gastrulation is completed. According to Kleinenberg, the meso-
blastic and neural elements are separated from the ectoblast in
a common basis (ventral plate) which is afterwards differentiated
to form a neural plate and a muscle-plate.

It is much to be regretted that neither Kleinenberg nor
Salensky has made a minute study of the posterior portion of
the germ-bands in surface-view. All of Kleinenberg’s illustra-
tions of the histological detail are made from sections, and a
careful study of them has not only left me unconvinced in regard
to the absence of teloblasts, but has given some ground for the
suspicion that he may have overlooked them —a suggestion
which I should not venture to make were it not for his previous
failure to see the eight anterior teloblasts in Lasmbéricus. Thus
he figures large cells with huge nuclei at the posterior ends of
the neural foundations in Asterope (No. 31, Taf. 14, Fig. 69)
and Alciope (l.c., Fig. 67"), which look extremely like sections of
the neuroblasts in Lumobricus ; and he figures in Fig. 68%, in
Asterope, a group of large cells at the hinder ends of the meso-
blastic bands, which, to say the least, deserve further study, for
it is possible that the mesoblastic condensation has not gone as
far as in Lumobricus, and that the two primary mesoblasts of this
form are represented in Asverope, etc., by a larger group.

The apparently ectoblastic origin of the mesoblast in forms
under consideration, is by no means irreconcilable with the facts
observed in the foetal types, though further researches are re-
quired to show their precise relations. The explanation must,
I believe, be sought in the relations of the posterior ends of the
germ-bands to the blastopore, a more precise study of which in
the Polychzeta is now of the greatest importance. All the evi-
dence goes to show that the primary mesoblasts arise on either
side the median line, near the posterior (ventral) lip of the

444 WILSON. [VoL. III.

blastopore, though owing to an acceleration of development,
they may be already differentiated in the blastula. After the
narrowing of the blastopore, this position is found to be anterior
to the anus (apparently latero-ventral) on either side the median
line—a position which very nearly corresponds to the seat of
mesoblast-formation at the hinder ends of the germ-bands in Lopa-
dorhynchus and similar types. There can be little doubt, there-
fore, that further study of the matter will show the germ-bands
of Lopadorhynchus, and its embryological allies, to have nearly the
same relation to the blastopore as in the other types, for the
evidence tends to show that the blastopore of all annelids occu-
pies at first the entire ventral surface. The seat of mesoblast
formation has, however, shifted slightly, having passed outward
from the lip of the blastopore, so as to lie, after closure of the
blastopore, in the ectoblast, and the apparent effect of this change
has been heightened by a retardation in the formation of the
mesoblast. Evidence is not wanting that precisely such a shift-
ing has taken place in other animals, usually, however, in con-
nection with the formation of a primitive streak, by coalescence
of the lips of the primitive blastopore. Such a case is that of
Phoronis (Caldwell, Nos. 11, 12), which is of special value in
this connection, since the primitive blastopore has the same
position as in annelids, closes in the same manner, and there
can be no question of the mesoblastic shifting. The blastopore
narrows to form the mouth, as in Lumdbricus, but a median ven-
tral “primitive streak” is left along the line of the closure,
where the layers remain for some time in fusion. The meso-
blast arises from three distinct centres of growth situated along
the primitive streak, but differing in their relation to it. The
anterior part is formed within the lip of the blastopore, and
hence from the entoblast, the middle part from the lip itself,
and hence from the indifferent cells of the primitive streak, the
posterior part just outside the lip, and hence apparently from
the ectoblast. There can be little doubt that these three modes
of mesoblast-formation were originally alike, and were after-
wards differentiated by slight changes of position with refer-
ence to the lipof the blastopore. It remains to be seen whether
a primitive streak can be found in the annelid embryo, but in
any case there can be little doubt that the apparent contradic-
tion between the two types of mesoblast-formation in annelid is

No. 3.] THE EMBRYOLOGY OF THE EARTHWORM. 445

due to a similar shifting of the seat of mesoblast-formation with
reference to the blastopore.

It appears impossible at present to determine the primitive
origin of the material now segregated in the primary mesoblasts,
for the extreme condensation of development involved in their
origin has completely masked the original mode of development.
There is, however, nothing in the history of the teloblasts to
preclude the hypothesis that the walls of the ccelomic cavities
were originally formed as a series of gut-pouches, as in Am-
plioxus. The primary mesoblasts lie at the extreme posterior
limit of the entoblast, and it is not difficult to picture the process
by which a series of gut-pouches, successively formed at the
posterior part of the archenteron, might be crowded further and
further back in development, until the present complete segre-
gation of the mesoblast in a single pair of the cells was attained.
(Cf. Hatschek, Zoologie, p. 76.) I will only add that if the
mesoblastic somites should ultimately be shown to be homolo-
gous with gut-pouches, and if my view of the homodynamy of
the prostomial and trunk-cavities be correct, the prostomial
cavity (z.e., the primary body-cavity of the Trochosphere), would
be comparable with an unpaired anterior diverticulum of the
alimentary canal (as in Guxzda and other Platyhelminthes), or
with one of the median chambers of the Actinozoa.

It is interesting to recall in this connection Bateson’s discovery
that the prostomial mesoblast in Sa/anoglossus is actually derived
from an unpaired median diverticulum of the archenteron ; and
the same author has shown that this diverticulum corresponds
closely with the anterior diverticulum in Amphiorus, though the
latter structure divides into right and left chambers at the time
of its separation from the archenteron.

Bryn Mawp, Pa., June, 1889.

C. METHODs.

After testing many different hardening fluids, I have found none to compare
with Perenyi’s fluid, which gives uniformly the best results, both for sections
and for surface-views of all stages, and is far superior to picro-sulphuric acid
or corrosive sublimate. Flemming’s mixture of osmic, chromic, and acetic
acids gives very clear differentiation of the middle stratum of the germ-bands
after staining with haematoxylin, but in most respects it is far inferior to Pe-
renyi’s fluid. The embryos were left in the fluid from 15 to 60 minutes,

446 WILSON. [VoL. III.
placed in 70 per cent alcohol for a day, and kept permanently in go per cent
alcohol.

For permanent staining no method has proved so satisfactory as borax-
carmine followed by hematoxylin. After being deeply stained in the carmine
(12 hours), and extracted in acid alcohol in the usual manner, the embryos
were treated with extremely dilute ammoniacal alcohol for a few minutes, to
neutralize the free acid, and were then stained in very dilute Kleinenberg’s
hematoxylin (12 hours or more). In case of overstaining with hematoxylin,
the color may be again extracted with acid alcohol, after which the specimens
are again treated with ammoniacal alcohol. This process, following treatment
with Perenyi’s fluid, gives beautifully clear preparations, which are specially
favorable on account of the clearness with which the cell-outlines are shown.
It has been found desirable to embed the specimens for sectioning, as soon as
possible after hardening, and to reduce the time of immersion in melted paraf-
fin to a minimum (Z.e., not more than Io or 15 minutes).

For surface-views of the germ-bands, the borax-carmine stain should be
very deep, and the hematoxylin very slight, so as to give the specimen only
a purplish color, not a dark blue. The germ-bands are dissected off on the
slide, in strong glycerine. This method has, in my experience, given far better
results than that of osmic acid followed by Merkel’s fluid, so successfully used
by Whitman in the study of Clepszne.

For the study of entire specimens of the young stages, I have found Pe-
renyi’s fluid followed by alcohol, water, very dilute iodine solution, and gly-
cerine, to give results superior beyond comparison to those attained by any
other method. The iodine colors the protoplasm pale yellowish brown, the
cell-outlines are clearly marked, and the nuclei are stained deep brown. In
time, most of the iodine is precipitated in the form of deep brown spheres,
which mar the clearness of the preparations, but such specimens may be after
wards stained with carmine, etc., sectioned and mounted in balsam in the
usual manner, and give perfect satisfaction, even after a stay of two years or
more in the glycerine.

LIST OF PAPERS REFERRED TO.

1. BALFouR, F. M. Comparative Embryology, I., II., 1880, 188r.

2. BaTeson, W. The Early Stages in the Development of Balanoglossus
(sp. incert.). Quart. Fourn. Micr. Sci., XXIV. 1884.

3. Id. The Later Stages in the Development of Balanoglossus Kowalevskii.
Quart. Fourn. Micr. Sct.. XXV. Supplement, 1885.

4. BEDDARD, F. Note on the Paired Dorsal Vessel of Certain Earthworms.
Proc. Roy. Phys. Soc., Edinburgh, VIII. 1885.

5. BEeRGH,R.S. Die Metamorphose von Aulastoma gulo. Aré. a. d. Zod)
Inst. Wiirzb., VII., 3. 1885.

6. Id. Die Exkretionsorgane der Wiirmer. Kosmos, 1885, II., 2.

7- Id. Die Entwickelungsgeschichte der Anneliden, etc. Kosmos, 1886,
EI. 6;

No. 3-.| ZHE EMBRYOLOGY OF THE EARTHWORM. 447

8.

28.

29.

30.

ar.

32.

Id. Zur Bildungsgeschichte der Excretionsorgane bei Criodrilus. Aré.
a. da. Zool. Inst. Wiirzb., VI1., 3. 1888. :

Bucinsky, Pet. Zur Frage uber die Entwickelung des Regenwurms.
Not. Neuruss, Naturf. Ges., VII. [Russian]. 1881 (¢. Exsig).

BuTscHul, O. Entwicklungsgeschichtliche Beitrage (I. Paludina vivi-
para). Zezt. f. wiss. Zool. 29. 1877.

. CALDWELL, W. H. Preliminary Note on the Structure, Development,

and Affinities of Phoronis. Proc. Roy. Soc., XXXIV. 1882.

. Id. Blastopore, Mesoderm, and Metameric Segmentation. Quart.

Fourn. Micr. Sct., XXV. 1885.

. CrLaus, C. Neue Beitrage zur Morphologie der Crustaceen. Ard. d.

Zool. Wien, V1., pp. 91-95. 1885.

. Dourn, A. Die Pantopoden des Golfes von Neapel. Fauna u. Flora

ad. Golfes von Neapel, 11. Monographie, pp. 85, 86. 188t.

. Frarpont. Le Genre Polygordius. Fauna u. Flora d. Golfes von

Neapel, XX1V. Monographie, 1887.
E1sic, H. Monographie der Capitelliden. Fawna u. Flora d. Golfes
von Neapel, XVI. Monographie, 1887.
FRIEDLANDER. Beitrage zur Kenntniss des Centralnervensystems von
Lumbricus. Zeztschr. f. Wiss. Zoél., XLVI. 1888.

. HATSCHEK, B. Studien iiber Entwicklungsgeschichte der Anneliden.

Arb. a. d. Zool. Inst., Wien, 1. 1878.
Id. Protodrilus Leuckartii. Ard. a.d. Zodl. Inst., Wien, Il. 1880.

. Id. Ueber Entwicklung von Sipunculus nudus. Ard. a. d. Zool. Inst.,

Wren, Vip it 1883.

. Id. Studien iiber Entwicklung des Amphioxus. <Aré. a. d. Zool. Inst.,

Wien, lV. 1884.

. Id. Zur Entwicklung des Kopfes von Polygordius. Ard. a. d. Zoil.

Inst., Wien, VI. 1885.

. Id. Entwicklung der Trochophora von Eupomatus Uncinatus. Ard. a.

ad. Zool. Inst., Wien, VI. 1885.
Id. Lehrbuch der Zodlogie, Jena, 1888.

. HERTWIG, O. and R. Die Ccelomtheorie. 1881.

KENNEL, J. Ueber Ctenodrilus pardalis, Clap. Ard. a. d. Zobl.-Zodt.
Inst. Wiirzb., V., 4. 1882.

. Kowa.evsky, A. Embryologische Studien an Wiirmern und Arthro-

poden. Mém. del’ Acad. Imp. de Sc. de St. Pétersbourg, XV1., No.
12.) 1671.

KLEINENBERG, N. The Development of the Earthworm. Quart.
Four. Micr. Sct., XIX. 1879. [Sullo sviluppo del Lumbricus trape-
goides, Napoli. 1878.]

Id. Suil’ origine del Sistema centrale degli Annelidi. Reale Acad. dei
Lincet. 1880-81.

Id. De lOrigine du Systéme Nerveux Central des Annélides. Arch.
Ital. de Biol., 1. 1882.

Id. Die Entstehung des Annelids aus der Larve von Lopadorhynchus.
Zeitschr. f. Wiss. Zool., XLIV. 1886.

LanG, A. Lehrbuch der Vergleichende Anatomie. Jena, 1888.

448 WILSON. [Vor. III.

33. Id. Der Bau von Gunda Segmentata. Jitth. a. d. Zovl. Stat. 2u
Neapel, Il. 1882.

34. METSCHNIKOFF, E. Beitrage zur Entwicklungsgeschichte einiger nie-
deren Thiere. Vorlauf, Mitth. im Bull. del’ Acad. Imp. de St. Péters-
bourg, XV. 1871. And in Mélanges Biologiques, VII.

35. Meyer, E. Studien iiber den KGrperbau der Anneliden, I-III. J7tth.
a. a. Zool. Stat. zu Neapel, VII. 1886.

36. Id. Studien uber den K6rperbau der Anneliden, IV. JZitth. a. d. Zool.
Stat. zu Neapel, VIII. 1888.

37. Rouve, E. Histologische Untersuchungen iiber das Nervensystem der
Polycheten. Zo0l. Beitrage, Breslau. 1887.

38. SALENSKY, W. Beitrage zur Entwicklungsgeschichte der Anneliden.
Biol. Centralot., U1. 1883.

39. Id. Etudes sur le développement des Annelides. Arch. de Biol., Il.,
IV. 1882, 1883.

40. SCHULTZE, O. Die Entwicklung der Keimblatter und der Chorda dorsalis
von Rana fusca. Zezt. f. Wiss. Zoobl., 47. 1888.

41. SEpGwick, A. Origin of Metameric Segmentation. Quart. Fourn.
Micr. Sci., XXIV. 1884.

42. SPENGEL, J. W. Oligognathus Bonellie. J7ztth. a. d. Zool. Stat. 2u
Neapel, Ill. 1882.

43. VEJDOvsKy, Fr. Ueber die Entwicklung des Herzens bei Criodrilus.
Sitzb. d. k. bohm. Ges. d. Wiss. 1879.

44. Id. System und Morphologie der Oligocheten. Prag, 1884.

45. Id. Die Embryonalentwicklung von Rhynchelmis. Sztzd. d. k. bohm.
Ges. d. Wvss. 1886.

46. Id. Das larvale und definitive Excretionssystem. Zodl. Anzeiger, X.
1887.

47. Id. Uber die Morphologie des Exkretionsapparates. Sztzb. d. Konigl,
bohm. Ges. ad. Wiss., Math.-natur Classe, 1887 [1888], p. 697. [In
Bohemian, but with several wood-cuts. |

48. Id. Entwickelungsgeschichtliche Untersuchungen, Heft. I. Reifung,
Befruchtung und die ersten Furchungsvorgange des Rhynchelmis-
Eies. Prag, 1888.

49. WELDON, W. F.R. On Dinophilus gigas. Quart. Fourn. Micr. Sci.,
DEGVille S87:

50. WuitTMAN, C. O. Embryology of Clepsine. Quart. Fourn. Micr. Scé.,
XVIII. 1878.

51. Id. The Germ-layers of Clepsine. Zo00l. Anzeiger, 1X., 1886, p. 171.

52. Id. Germ-layers in Clepsine. ourn. Morph., 1. 1887.

53. WILson, Edm. B. Development of Renilla. Phzl. Trans. 1883.

54. Id. Germ-bands of Lumbricus. ourn. Morph., 1. 1887.

No. 3.] ZHE EMBRYOLOGY OF THE EARTHWORM.

449

EXPLANATION OF PLATES.

Reference Letters.

ar. Archenteron, ms. Mesoblastic cells.
6, Blastopore. m. ms. Migratory mesoblast.
c.g. Cephalic ganglia. mc. Muscle-cells.
c.¢. Ciliated cells of the ventral sur- JV. Nephroblast.
face. Vb. Neuroblast.

Cephalic mesoblast,

. Neural cord.

c. p. Cleavage pore. np. Nephridium.
ce. Ccelomic cavity. np. c. Nephric cord.
d. Dissepiment. @, ¢c. (Esophageal collar.
ec. Ectoblast. p. Proctodeum.
en. Entoblast. p.¢. Prostomial or cephalic cavity.
f- Funnel of nephridium or funnel- S. Seta.
cell. s. ¢. Segmentation cavity.
g: 6. Germ-band. s. gl. Setigerous gland.
g. Ventral ganglion. s. m. Somatic mesoblast.
z. Investing cells of nephridia. sp. Splanchnic mesoblast.
7, v. Lateral vessel. st. Stomodzeum.
Z. Lateral teloblast. 5.2 Schluckzellen or larval excretory
2. c. Lateral cell-cord. organs.
MM. Primary mesoblast. v. 2. v. Ventro-lateral vessel.

Mouth,

. Wentral vessel,

450 WILSON.

EXPLANATION OF PLATE XVI.
Lumbricus fetidus.

Fic. 1. Unsegmented ovum, surrounded by the vitelline membrane, with two
groups of polar cells.

Fic. 2. First cleavage (in the plane of a group of polar cells).

Fics. 3 TO 5. Four-celled stage, showing the segmentation cavity.

Fics. 6 AND 7. Two succeeding stages, showing the division of the large cell into
two equal parts, followed by a division of one of the three smaller cells.

Fics. 8 AND 9. Two views of another specimen in the six-celled stage (the indi-
vidual cells numbered for identification).

Fics. 10 AND II. Two views of a seven-celled embryo.

Fics. 12 AND 14. Three views of an eight-celled stage.

Fics. 15 TO 19. Various views of a blastula (optical section in Fig. 19), consisting
of thirteen cells, showing the entire structure. The protoplasmic prominence marked
x, attached to cell No. 4 (which is probably accidentally caused) serves to orient the
embryo.

Fic. 20. Later blastula with a large segmentation cavity but no cleavage-pore.

Fics. 21 AND 22. Surface-view and optical section of a blastula somewhat younger
than the last, showing the cleavage-pore.

Fic. 23. Surface-view of blastula, showing the two primary mesoblasts at the
surface.

(All the figures drawn with the camera from preserved specimens. Enlarged 300
diameters.)

, Gynt

452 WILSON.

EXPLANATION OF PLATE XVII.
Lumbricus fetidus.

Fics. 24 TO 30. Series of optical sections showing the early history of the meso-
blast. Figs. 24, 26, 27 are side views; Figs. 29 and 30 horizontal views; Fig. 28 is
an oblique lateral view of the same specimen shown in Figs. 27 and 29. The series
shows the gradual enclosure of the primary mesoblasts within the segmentation cavity,
the beginning of the mesoblastic cell-rows and the variation of the cleavage-pore,
which is absent from Figs. 24, 25, and 30, but present in the others. The mesoblastic
rows meet in front.

Fics. 31 AND 32. Dorsal and lateral views of a blastula in which the flattening
preparatory to invagination has begun. The layers are already clearly differentiated,
there is a large segmentation cavity, and the mesoblastic rows still meet in front.

Fic. 33. Dorsal view of a slightly later stage (cf Figs. 34, 39, 40, 45, 46), show-
ing the entoblast, the ectoblast in optical section at the sides, the ectoblastic nuclei
of the dorsal surface, and the primary mesoblasts.

Fic. 34. Ventral view of the same embryo, showing the entoblast nuclei and the
edge of the ectoblast.

Fic. 35. Ventral view of early gastrula (the anterior extremity directed upwards),
showing the ectoblast at the sides and below, the entoblast, and the extreme anterior
end of the right mesoblastic row in optical section at 7. s.

Fic. 36. Gastrula, ventral view, showing the blastopore, the anterior ends of the
ectoblastic part of the germ-bands (ec.), and the nuclei of the flattened cells of the
ventral ectoblast.

Fic. 37. Corresponding view of another specimen in which the lateral infolding
has advanced more rapidly than in the last, so as to give rise to a slit-like blastopore.
(Compare Fig. 42. For actual section of this specimen, see Fig. 52.)

Fic. 38. Lateral view of established gastrula in which the mesoblastic bands have
met above the mouth. The left primary mesoblast (JZ) and mesoblastic band (ms.)
shown. Archenteron and ectoblast in optical section. Limit of ectoblastic part of
the germ-band indicated by the faintly drawn nuclei. (Compare Fig. 43.)

Fic. 39. View of flat gastrula (shown in Fig. 33) from the right side, showing the
ectoblast, entoblast, and one primary mesoblast in optical section, and also the ecto-
blastic nuclei of the right side. (For actual sections of the same specimen, see Figs.
45 and 46.)

Fic. 40. The same specimen in transverse optical section, showing the mesoblastic
bands (vs.) at the sides.

Fic. 41. Surface view from the left side and below, of the specimen shown in Fig.
36. Only the ectoblastic part of the germ-band is shown, except the primary meso-
blast (JZ). Ectoblast in optical section at the sides.

Fic. 42. Lateral view of gastrula at about the same stage as Fig. 37, showing the
right mesoblastic band (superficial ectoblast not shown).

Fic. 43. Anterior view of the embryo shown in Fig. 38 (slightly diagrammatic),
to show the anterior union of the germ-bands above the mouth and their approxima-
tion on its ventral side.

Fic. 44. Dorsal view of the embryo shown in Fig. 42, showing the archenteron,
the lateral ectoblast, the primary mesoblasts lying in contact in the middle line, and
the two mesoblastic rows (77s.).

Fics. 45 AND 46. Longitudinal (actual) sections from a complete series of the
embryo shown in Figs. 33 and 39._ Fig. 45 is towards the side and shows the right
mesoblastic band in nearly its whole extent. Fig. 46 is nearly in the median line,
passing through one of the primary mesoblasts. ‘The segmentation cavity has disap-
peared. The series shows beyond question that the mesoblastic bands are separate in
front. No trace of the Schluckzellen can be seen.

(Enlargement 300 diameters. All the figures with the camera excepting Nos. 32,

39, and 40.)

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Journal of Morphology. Val. M.

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any.

454 WILSON.

EXPLANATION OF PLATE XVIII.

(Nos. 47 to 52 and 57, 58 from Z. fetidus, Nos. 53, 54, L. communis, Nos. 55, 56
from an unknown fresh-water oligochzete, the embryos of which are in all essential
features like those of Lumbricus.)

Fic. 47. Right ventro-lateral view of an embryo at the earliest period in which the
mesoblasts and nephroblasts are distinguishable. Right germ-band in surface view,

left in optical section. X 300.
Fic. 48. Right lateral view of embryo with completely established germ-bands,
showing position of the teloblasts, cell-rows, etc. xn70)

Fic. 49. Ventral view of the same embryo. The germ-bands wholly separate be-
low. (Outlines with camera. Cells diagrammatic.)

Fic. 50. Right lateral view of older living embryo, showing the stomodzum, ar-
chenteron, the ccelomic and prostomial cavities, developing nephridia, and the dissepi-
ments. The most anterior of these (¢!) form the ventral and later also the posterior
boundary of the prostomial cavity. x 170;

Fic. 51. Left lateral view of embryo in the middle period of development. The
anterior teloblasts have broken up (see Fig. 63 for diagram of the germ-bands); the
primary mesoblasts remain. The dorsal limit of the mesoblast is marked by the lat-
eral vessel (/. v.), which ultimately coalesces with its fellow to form the dorsal vessel.

<0:

Fic. 52. Transverse (actual) section through the embryo shown in Fig. 37. The
mesoblastic bands are quite distinct from the ectoblast through their whole extent,
and are now widely separated in front. X 300.

Fics. 53 AND 54. Transverse (slightly oblique) section through an embryo at a
somewhat earlier stage than Figs. 48, 49. No. 54 (the more posterior) passes through
the primary mesoblasts (which appear on the apparent dorsal side owing to the great
curvature of the bands) and the two nephroblasts of the left side. No. 53 cuts the
left mesoblast (/Vé.), the left (double) nephric cord, and one of the right nephro-
blasts. All these teloblasts lie at the surface. X 300.

Fics. 55 AND 56. Two consecutive horizontal sections through the anterior region
of an embryo in which the prostomial cavity has just appeared. In No. §5 (more
dorsal) the extreme anterior part of the mesoblast appears, and the bridge of neural
tissue (apparently fused with the ectoblast) that joins the two cephalic ganglia. In
No. 56 the prostomial cavity appears, lying between the cephalic ganglia. In the
following section this cavity disappears, and the dorsal wall of the stomodzum
appears. eR

Fics. 57 AND 58. Two transverse sections through the anterior part of an older
embryo. No. 57 (the more anterior) shows the prostomial cavity and the dorsal wall
of the stomodeum. No. 58 (two sections further down) shows the anterior corners
of the anterior pair of ccelomic cavities, with the prostomial cavity between them.

X 300.

(All the figures with the camera.)

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456 WILSON.

° EXPLANATION OF PLATE XIX.
Fig. 61, Z. communis; Fig. 62, L. terrestris ; the others from Z. fetidus.

Fic. 59. Superficial view of the posterior termination of the neural and nephric

cell-rows of the left germ-band, showing the division of the neuroblast. X 700.
Fic. 60. The primary mesoblasts and beginning of the mesoblastic rows in a speci-
men of the same age as the last. X 450.
Fic. 61. Superficial view of right germ-band, showing the four teloblasts; the
nephroblasts dividing. X 375:
Fic. 62. Similar view of left germ-band of Z. terrestris. X 375.

Fic. 63. Diagram of the hinder part of the germ-bands of an embryo in the stage
shown at Fig. 51. The bands are spread out flat, and all their elements are shown.
The lateral cell-cord cannot be distinguished from the general ectoblast. X 250.

Fic. 64. Superficial view of part of the left germ-band of Z. fetidus to show
division of nephroblast. The nuclei of the superficial ectoblast are accurately drawn,
and are seen directly to overlie the teloblasts and cell-rows. X 700.

Fic. 65. Surface view of the germ-bands at a late stage at the point of divergence
behind. Below the horizontal line the focus is quite superficial, in front of it the cells
of the various rows are shown, separated here and there by deeper-lying ectoblast
cells (e.c.). At the right appears the edge of the mesoblastic band (ms.) lying at
a somewhat deeper level. The lateral cord is indistinguishable. X 400.

(All the figures with the camera from preserved specimens. )

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EXPLANATION OF PLATE XX.
Lumbricus communis.

Fics. 66, 67, 68. Three cross-sections from the same series with Nos. 53 and 54
(Pl. XVIII.). Fig. 66 is next to No. 54, and passes through the outer nephroblast on
the left side. Fig. 67 is two sections anterior to No. 53, and passes through the right
neuroblast and lateral teloblast (one of the nephroblasts of this side is shown in Fig.
53, and the other appears in an adjoining section). Fig. 68 is several sections further
forward. X 300.

Fic. 69. Cross-sections through a slightly later stage (cf Fig. 94, Pl. XXII.), show-
ing the cleavage of the mesoblast. X 300.

Fic. 70. Adjoining section from the same series in the region of a dissepi-
ment. X 300.

Fic. 71. Cross-section of germ-bands, a little later than the last. The neural rows
are entirely covered by the ectoblast. The nephric rows still lie at the surface. The
lateral rows cannot clearly be distinguished. X 400.

Fic. 72. Cross-section through the posterior part of an embryo at about the stage
of Fig. 51, to show the dorsal extension of the germ-bands by migration, the middle
stratum, the longitudinal muscle-bands, and the longitudinal vascular trunks. X 225.

Fics. 73 To 78. Tangential longitudinal sections (somewhat oblique) from a series
which shows the entire course of the mesoblastic and neural rows, with the correspond-
ing teloblasts, the origin of the cephalic ganglia, head-mesoblast and Schluckzellen
(see p. 415). The right primary mesoblast and the right neuroblast appear in No. 73;
the left mesoblast in No. 75, the hinder part of the left mesoblastic band and the
anterior part of the right in No. 77; the left mesoblast in Fig. 78, which passes
through the middle line in front. X 300; No. 76, X 400.

(All the figures with the camera.)

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460 WILSON.

EXPLANATION OF PLATE XXI.
Figs. 82, 85, from Z. fetidus ; Fig. 83 from L. terrestris ; the others from LZ. communis.

Fic. 79. Sagittal section of anterior part of an embryo shortly after the appearance
of the head-cavity and the union of the cephalic ganglia. The remains of the
Schluckzellen shown at S.Z. *K 225.

Fic. 80. Corresponding sections through a later stage, in which the first pair of
ccelomic cavities have come together behind the cephalic cavity at ca, the first dis-
sepiment shown at D. X 225.

Fic. 81. Sagittal sections through a still later stage, in which the cephalic ganglia
have separated from the ectoblast and begun to travel backwards; the prostomial
cavity is nearly filled with a network of mesoblastic cells; the cesophageal gland

cells at g7. < 225,
Fic. $2. Sagittal section of young embryo of Z. fetidus to show the thickened
lower lip s. Z. of the stomodzeum. 225:
Fic. 83. Longitudinal section through the nephric cord and developing nephridia,
showing their relation to the dissepiments and coelomic cavities. X 400.
Fic. 84. Corresponding section through Z. communis. X 400.

Fic. 85. Surface view (from within) of developing nephridia and setigerous gland.
The lateral limits of the nephric cord are defined by the longitudinal muscular
bundles (72. ¢.). X 700.

Fic. 86. Longitudinal section through developing nephridia (somewhat older than
in Fig. 84), and setigerdus glands, showing their relations to the nephric cords, etc.
The section is slightly oblique, and passes in front into a longitudinal bundle of muscle-

fibres (mm. ¢.) (which now overlaps the margin of the nephric cord). X 400.
Fic. 87. Longitudinal section through still older nephridia. X 400.
Fic. 88. Corresponding section of a later stage, in which the setz can be dis-

tinguished. The nephric cord can no longer be made out in front. X 400.

(All the figures with the camera.)

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EXPLANATION OF PLATE XXII.
Fig. 89 from rea fetidus ; the others from Z. communis.

Fic. 89. Surface view of part of the dorsal wall of an embryo in the stage of Fig.
50, showing a few of the large ectoblast cells (or their nuclei), the branching muscle-
cells and the amceboid cells (1) of the migratory mesoblast. ’ X 400.

Fic. 90. Part of cross-section through posterior part of an embryo of about the
same age as Fig. 51, in the region where concrescence of the neural cords is in prog-
ress; the section passes through the commissures, and the neural rows are com-
pletely separated from one another. X 400.

Fic. 91. Section from the same series two sections behind the last, in the re-
gion of a pair of ganglia; the neural rows are connected above by a bridge of neural
tissue. X 400.

Fic. 92. Longitudinal section (drawn by combining sketches of two adjoining sec-
tions) a little to the side of the one shown in Fig. 80, showing the ciliated canal of
the head-kidney embedded in the dorsal wall of the archenteron. X 400.

Fic. 93. Longitudinal section showing the setigerous glands, dissepiments, ventro-
lateral blood-vessels and portions of the nephridia in a stage about like that shown in
Fig. 51. X 300.

Fic. 94. Sagittal section through the posterior part of an embryo (like Fig. 51)
shortly before the formation of the proctodeeum, The neural rows end abruptly be-
hind, and the primary mesoblasts are the only teloblasts remaining. X 300.

Fic. 95. Section from posterior part of a transverse series of an embryo just before
hatching. Owing to the upward curvature of the hinder part of the body, the sec-
tion passes nearly horizontally through the germ-bands. The mesoblastic bands are
in contact at their hinder ends; the lateral cell-rows end abruptly behind. X 225.

Fic. 96. Section from the same series, five sections further forward, cutting the
hinder part of the germ-bands transversely and the proctodzal invagination vertically.
The primary mesoblasts have disappeared; the mesoblastic bands can be traced
around the proctodeum and meet on the dorsal side. Sar225-

Fic. 97. Sagittal section (corresponding precisely to No. 94, but a little further
toward the side) passing through one of the mesoblastic bands and through the broad
proctodzeal invagination. The latter is deepest ventrally and fades away towards its
anterior lip. The tip of the mesoblastic band represents the former position of the
primary mesoblast. ‘i X 350.

(All of the figures drawn with the camera.)

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Journal of Morphology. Vol M.

ON THE MORPHOLOGY: OF RIGS AND THE FATE
OF THE ACTINOSTS On tHE jie DEAN
FINS IN: FISHES.

Dr. G. BAUR,

New Haven, Conn.

In a paper read before the American Association for the
Advancement of Science, two years ago, I reached the follow-
ing conclusions on the ribs of vertebrata :'—

“1, The ribs are developed detween the myocomata ; they are
therefore zxtervertebral.

2. The ribs are originally one-headed and connected with
well-developed intercentra.

3. All forms and connections of the other ribs can be derived
from that condition.

4. The lower arches of the caudal vertebre are either formed
by true ribs, the oldest fishes (Ganoidei, Dipnoi), or by processes
of the intercentra (Teleostei, Stapedifera).

5. The connection between the Dipnoans and the Stapedifera
is still missing.

6. Some remarks on the nomenclature of the elements of
the vertebral column.

Owen’s names, ‘neurapophysis’ and ‘pleurapophysis,’ are
not correct ; the neural and pleural arches are no processes of
the vertebrz, but are distinct parts.

The two elements composing the neural arch ought to be
called the zeuvoids; the two elements composing the pleural
arch, the pleurozds.

The spines connected with the neuroids ought to be called,
as before, zeural spines; those connected with the pleuroids,
pleural spines.

The real centrum of the vertebra ought to be called centrum ;
the lateral elements composing it, hemzcentra (Albrecht), not
pleurocentra.

The name intercentrum ought to be preserved.”

1 Baur, G. On the Morphology of Ribs. American Naturalist, October, 1887, p. 45.

464 BAUR. [Vot. III.

I have nothing to change in these general results, but can
add some important facts relating to numbers 4 and 5.

The connection between higher vertebrates and fishes is found
to be the condition represented by LEPIDOSTEUS.

Up to this time the difference in the tail of fishes and the
higher vertebrates appeared to be a fundamental one. In fishes
the “hamal arches” which enclose the subcaudal blood-vessels
are either formed by true ribs, or by the prolonged parapophyses
to which the ribs are united. In all higher vertebrates the ribs
are entirely separated from the ‘“hamal arches”; they are
placed above these on the side of the vertebrae. The following
diagrams represent the two conditions :—

al m, neuroid.
( )p wa C™~ _ A; parapophysis.
P pl, pleuroid
, pleuroid.
pl a a, chevron,
I 2.

1. Caudal vertebra of Fishes.
2. Caudal vertebra of higher Vertebrates.

It is evident that the “hamal arch” of fishes, which is either
composed of pleuroids, or of pleuroids and parapophyses, can-
not be the homologue of the “ hzmal arch” of the higher ver-
tebrates. The question is, what elements of the fish’s skeleton
are used in the formation of the “hzmal arch” of the higher
vertebrates; in other words, what are the homologues of the
chevron bones ?

The original condition is, that the subcaudal blood-vessels are
surrounded by the pleuroids, in the same way as the neural
cord is surrounded by the neuroids. In the higher vertebrates
the pleuroids have moved dorsad, and have become entirely
independent from the blood-vessels. In fishes the pleuroids are
connected with the parapophyses (“ Basalstuempfe’”’ Goette) of
the vertebra. The condition found in the higher vertebrates
could be developed by two different ways: either the parapo-

No. 3.] MORPHOLOGY OF RIBS. 465

physes move dorsad together with the pleuroids (in this case the
chevrons cannot represent parapophyses), or the pleuroids alone
begin to move, separating from the parapophyses, which would
form the chevrons. The latter opinion was held by me until now.
The examination of Lepzdosteus shows that this view is incorrect.
There are forty prze-anal vertebra in a skeleton of Lepzdosteus
osseus L. before me. From the second we find well-developed
parapophyses to which strong pleuroids are articulated. In the
most posterior vertebre the pleuroids begin to bend downwards
and the parapophyses become a little smaller. The 41st ver-
tebra shows the following conditions: The pleuroids are con-
nected with parapophyses and are directed downwards; between
the two pleuroids a strong element ts placed which nearly touches
the centrum of the vertebra, and which supports the subcaudal
blood-vessels ; this strong element ts the first well-developed acti-
nost of the anal fin. It is very strong proximally, differing from
the actinosts of other fishes in this regard. In the 42d vertebra
we have similar conditions. The second well-developed actinost
is below the vertebra supporting the subcaudal blood-vessels,
but it is not so strong proximally as the first; the ribs are not
directed downwards, but backwards, and are entirely separated
from each other. We have about the same characters in the
next four vertebrz. In the 43d and 44th the pleuroids are
turned backwards. The 43d is connected with one actinost, the
44th with two; the actinosts become very. thin proximally,
resembling the free actinosts in other fishes. The relation of
actinosts and vertebrae becomes loose. There are in all eight
well-developed actinosts of the anal fin; the anterior and pos-
terior ones are rudimentary ; these eight actinosts are in relation
to six vertebrz. In the 45th and 46th vertebre the ribs begin
to turn downwards again, touching each other distally, at the
same time they enclose the subcaudal blood-vessels. The same
condition we have in all the following vertebra, in which the
distal parts of the pleuroids co-ossify and become very strong.
These distal parts contain also the actinosts of the caudal fin.

The anterior part of the post-anal portion of the tail in Lept-
dosteus shows the condition of the higher vertebrates, the posterior
part that of fishes.

The Batrachia (Amphibia) developed from forms in which
the process, which begins at the anterior part of the post-anal

466 BAUR. [Vo.. III.

portion of the tail in Lepzdosteus, had been carried through the
whole tail. The form from which the Batrachia started must
have had a continuous anal and caudal fin, with well-developed
actinosts free from the ribs. Zhe chevron bones are the actinosts
of this continuous fin.

The following diagrams show different vertebrzee from the
posterior part of the vertebral column in Lepzdosteus : —

S Q ty y i

g Y
I. 2: By 4.
pf, parapophysis. /, pleuroid. a, actinost.

I. 40th vertebra of Zepidosteus. 4. 48th vertebra of Lepidosteus.
2. 4Ist vertebra of Lepidosteus. 5. 53d vertebra of Lepzdosteus.
3- 43d vertebra of Lepidosteus.

So far it has been the opinion that the elements of the anal
and caudal fins of fishes had disappeared entirely in the higher
vertebrates; but now we have shown that the elements of these
fins do not disappear, but are represented by the chevron bones of
the tail vertebra, which are the partial homologues of the actt-
nosts.| The actinosts of the dorsal fin and the upper part of the
caudal fin became probably united with the neuroids, and have
undergone reduction afterwards. That the anterior and posterior
paired fins of fishes, the anterior and posterior limbs of verte-
brates in general, are the result of fusion of actinosts of a con-
tinuous lateral fin, there seems to be little doubt.

Sept. 19, 1889.
1 The proximal part of the chevron above the subcaudal blood-vessels represents

the intercentrum, the distal part the actinost. In all higher vertebrates the intercen-
trum and the actinost are united.

ON THE MORPHOLOGY OF THE VERTEBRATE-
SKULE.

Dr. G. BAUR,

New Haven, Conn.

Ey Lae, “Orc ELEMENTS:

In this article attempts will be made to show that the doc-
trine of the “otic” bones established by Professor Huxley
twenty-five years ago, and held since that time by nearly all
morphologists, is incorrect. The material upon which these
notes are based consists of the skulls of Lepzdosteus, Amita,
Necturus, Mastodonsaurus, Chelone, Ichthyosaurus, Sphenodon,
Didelphys. Taking Chelone as a central form, I shall then
examine first the higher and afterwards the lower types.

In Chelone the foramen magnum is bounded laterally by the
exoccipitals ; to these bones the paroccipitals (Owen), opistho-
tics (Huxley) are united by suture on the outside. In front of
the paroccipitals another pair of bones is found, the petrosals
(Owen), proédtics (Huxley). The supraoccipital joins the paroc-
cipitals and petrosals, forming the characteristic Y-shaped fig-
ure. Between the paroccipital and the petrosal at the lower
side, the stapes is placed, which is small in comparison with the
surrounding bones.

In /chthyosaurus! we have about the same conditions: the
petrosal is a small bone; there are no true sutures between this
element, the paroccipital, and supraoccipital, they are all sepa-
rated by cartilage, which is very much more developed than in
Chelone. The stapes is exceedingly large, surpassing in size not
only the petrosal, but also the paroccipital; it is placed be-
tween paroccipital and petrosal below.

In Sphenodon we have a corresponding arrangement. In the

1 My observations on Ichthyosauria are mainly based on the splendid material in
the collection of Mr. A. N. Leeds of Eyebury, near Peterborough, England, in which
the elements of the skull are separated. I have to thank Mr. Leeds very much for
his great kindness and hospitality, shown to me during a visit two years ago.

468 BAUR. [Vot. III.

old animal supraoccipital, exoccipitals, paroccipitals, petrosals,
are united, but in the young all these elements are free. There
is much cartilage between the supraoccipital and the petrosal
and paroccipital. The paroccipital is united to the exoccipital
by suture; the elements in question.of a young Sphenodon}
resemble those in Chelone and especially in /chthyosaurus. In
all other Monocondylia the paroccipital is united very early to
the exoccipital, forming the paroccipital process of this element.
In all, the stapes is placed between the paroccipital and petrosal,
and becomes more and more reduced in size. In Sphenodon
it is of relatively large proportions.

In Didelphys the paroccipital is free from the exoccipital, but
united with the petrosal. This complex, for which the name
“‘periotic”’ has been introduced, is suturally united with the
squamosal, in which the quadrate and quadratojugal is also con-
tained. The stapes is between paroccipital and petrosal and
very small.

Now let us consider for a moment the supraoccipital. Ac-
cording to Professor Huxley this bone in the Monocondylia
contains on each side an element which is said to be free in the
embryo. In all the Monocondylia (except the Theromora, of
which nothing is known as to the point at issue) the supraoc-
cipital receives on each side the upper semicircular canals to a
smaller or greater degree; this we find in the lowly organized
Ichthyosaurus and in the highly specialized Bird. But these
canals are not lodged in a peculiar element confluent with the
supraoccipital on each side, called efzotzc by Professor Huxley,
but in the swpraoccipital itself.. The part of the supraoccipital
containing the canals never develops from a distinct centre of
ossification. There is no indication of it in the /chthyosaurus
and young Sphenodon, in which the supraoccipital is very small.
I thought to find this element in the Testudinata, in which the
paroccipital remains always free, but in embryos of Cheloniide,
Chelydridz, Trionychidz, Emydide, I failed to do so.

In Mammals the upper semicircular canals do not reach into
the supraoccipital.

As result of the examination of the skulls of the higher forms

1 I am very much obliged to Prof. B. G. Wilder, of Ithaca, for a young specimen

of Sphenodon \ent for examination. This animal forms in a half-adult stage a won-
derful specimen for a basis of osteological studies,

No. 3.] VERTEBRATE-SKULL. 469

we may state the following: There are always to be found three
elements in connection with the ear, the paroccipital, petrosal,
and stapes; the stapes, very large in the lower types (/chthy-
osaurus) becomes more and more reduced in size, ascending to
the higher types. A fourth element, the supraoccipital, takes
part in the Monocondylia, but not in the Mammals.

Passing now to the examination of the lower forms (Vecturus,
Mastodonsaurus, Amia, and Lepidosteus), in Necturus the fora-
men magnum is bound by the small exoccipitals; on the outer
side of these are the free paroccipitals, then follow in front the
large stapes and the petrosal. The same condition can be seen
in Proteus, the other living representative of the Proteida; but
in the other Batrachia the paroccipitals are co-ossified with the
exoccipitals.

In the Stegocephalia! we have exactly the same: in some of
the genera (Cyclotosaurus) the paroccipital is free from the exoc-
cipital; in others (Mastodonsaurus) it is co-ossified with the
exoccipital. The paroccipital is in relation to a dermal plate,
which is very improperly called the “epiotic.”’ I propose the
name “ pavoccipital plate’ for it.

Turning now to Amza,* we find the exoccipitals very large;
on the upper and outer side of these a small bone is seen, which
corresponds exactly to the paroccipital in Cyclotosaurus ; it is
also in relation to a dermal plate, and there is no doubt that
this small bone is the true homologue of the paroccipital in the
Batrachia and higher Vertebrates. Between the extensive
petrosal and the exoccipital a large but thin bone is found, the
“amtercalare”’ of Vrolik. ‘

In Lefidosteus the conditions are about the same, but there
is no bone between the petrosal and exoccipital, corresponding
to the intercalare. If this bone is removed in Ammza, we have
the arrangement of Lefzdosteus. In Amza the paroccipitals
take no part in the formation of the semicircular canals, but
they do in Lefpidosteus.

1 It is to be regretted that my friend, Dr. E. Fraas, did not give much attention to
morphological questions in his extensive work on the Labyrinthodontia of the Trias,
for which he had a wonderful material at hand; my determinations are mostly based
on his text and figures.

2 My thanks are due to Prof. Ramsay Wright of Toronto for a splendid specimen
of Amia, presented for examination.

470 BAUR. [Vor. III.

The question now is, what is the homologue of the interca-
lare? It is absent in all forms in which the cranium is not or
only little ossified, the Holocephali, Selachii, Dipnoi, Chondros-
tei. In Polypterus, the living representative of the Crosso-
pterygia, the intercalare appears to be a large element, in which
the paroccipital may be contained. I have not examined this
form. From the papers of Agassiz, Mueller, and Traquair, I
could not form an exact opinion, but from notes and drawings
very kindly sent to me by Dr. E. Koken of Berlin, I have
reached the conclusion that Po/ypterus is an aberrant form, the
morphology of which is not yet fully understood. In the Amii-
dz the intercalare appears for the first time, and from this
family the “Teleostei” have partially inherited it. Fossil fishes
do not throw any light upon this question.

We have seen that in the lowest “ Stapedifera”’ the stapes is
largest, and that it becomes more and more reduced in the
higher forms. There can be no doubt that the ichthyic an-
cestors of the Batrachia must have possessed an element
corresponding to this well-developed stapes. I think that the
intercalare represents this element. The stapes is a true bone
of the cranium; it is not formed by any part of the visceral
arches in the Batrachia, and all such connections in the higher
forms must be considered as secondary. It is possible to
understand now why the opinions on the origin of the stapes
differ so immensely.

The “tympanic bone” in Mammals has no homologue in the
Monocondylia, with the exception of some Birds where a similar
structure is to be seen (Psittaci, part); it is very small in the
Monotremata and becomes specialized in the higher groups.
The opinion of Peters and others, lately defended by Dr. H.
Gadow, that the tympanic represents the quadrate, cannot,
I think, be adopted. There seems to me to be very little doubt
that the quadrate of Mammals is represented by that part of
the squamosal to which the lower jaw is articulated, since we
have the same condition in the Theromora, which are nearest
the ancestors of Mammals.

I append, in a tabular form, the views of Professor Huxley
and myself, side by side.

No. 3.]

The paroccipital, Owen, of fishes
is called by Professor Huxley ‘ epi-
otic,” and considered the homologue
of the ‘‘ epiotic” in Labyrinthodon-
tia; the homologue of that portion
of the supraoccipital which lodges a
part of the upper semicircular canals
in the Monocondylia; the homologue
of one part of the squamosal in
Mammals.

The petrosal of Owen and former
authors is called ‘‘ prodtic” by Pro-
fessor Huxley.

The “intercalare” (Vrolik) in fishes
is called by Professor Huxley opzstho-
tzc, and considered as the homologue
of the paroccipital in the Monocon-
dylia.

Aug. 30, 1889.

VERTEBRATE-SKULL.

471

The Jaroccipital, Owen, of fishes,
is the paroccipital in Batrachia and
Monocondylia and the ‘‘ mastoid”
portion of the squamosal in Mam-
mals. The paroccipital of the Ba-
trachia is free in the Proteida, but
co-ossified with the exoccipital in the
other living representatives. In the
Stegocephalia it may be free, or unit-
ed with the exoccipitals. The so-
called ‘‘ epiotic”” in the Stegocephalia
is only a dermal plate covering the
paroccipital, which ought to be named
the paroccipital plate.!

The supraoccipital of the Mono-
condylia consists of this element alone,
and not of more.

I retain the name Zetrosal.

The “intercalare” (Vrolik) in fishes
is the homologue of the stapes in all
higher vertebrates, and the name in-
tercalare ought to be used in prefer-
ence to columella or stapes for all
vertebrates.

2. THE TEMPORAL ARCHES.

In the oldest Batrachia, the Stegocephalia, we find a continu-
ous dermal covering of the upper and lateral parts of the skull.
This covering is interrupted by five openings, —the two nasal
openings, the orbits, and the single parietal foramen: the same
conditions we have to expect in the ichthyic ancestors of the
Batrachia ; forms like Lepzdosteus would express such a stage.
The dermal bones of such a skull have been developed from
scales, and must have been very numerous at first ; later blend-
ing of elements, or enlargement of some at the cost of others,
took place, and the number was reduced. In the Stegocephalia
the number of these dermal ossifications is nearly constant.
The bones which interest us in the question about the temporal
arches are the following: parietals, frontals, post-frontals, post-

1 Among the Monocondylia the paroccipital is free in the Ichthyosauria and
Testudinata, but united with the exoccipital in the rest.

472 BAUR. [Vou. Ill.

orbitals, supratemporals, squamosals, jugals, quadratojugals,
supraoccipital and paroccipital plates (epiotics). In some of
the Stegocephalia another plate is found between the postorbital
and the frontal (A/e/anerpeton) ; this we have to consider as the
vestige of one of the more numerous plates of the ancestors of
the Stegocephalia.

In the oldest Testudinata we have also a complete bony cov-
_ering, but the number of elements has been reduced from 22 in
Melanerpeton to 12in Chelone. Thereare no distinct postorbitals,
supratemporals, supraoccipital and paroccipital plates. This
condition we still find in living forms like the Cheloniidz and
Dermochelydida. From such forms the Chelydridz, Dermate-
mydide, Staurotypidz, Cinosternide, Platysternide, Emydide,
Testudinidz, Trionychia, developed by losing the connection
between the squamosal and parietal,—in other words, by los-
ing material from behind. But at the same time a reduction
took place from below, between quadrate and jugal. The result
was the formation of a more or less slender arch between the
orbit and the quadrate. In a few cases this arch became
entirely reduced, — Terrapene, Geemyda.

In the Pleurodira two kinds of reductions took place; one
from below, which destroyed the connection between orbit and
quadrate, but retained that between squamosal and parietal.
This we see in the Chelydide; in Chelodina even the connec-
tion between squamosal and parietal has gone. The total
absence of a temporal arch in Zerrapene and Gewmyda on one
side, and of Chelodina on the other, is the product of two differ-
ent kinds of reduction. The first is produced by reduction from
below and behind ; the other by reduction from below only.

In the Sternothzeridz and Podocnemididz a reduction takes
place from behind and below, as in the Chelydrida. In none of
the Testudinata is a true supra- or infratemporal fossa developed ;
there is only one arch which represents the whole complex
between parietal, frontal, and jugal, quadratojugal.

The complete covering of the skull is for the first time inter-
rupted in the Ichthyosauria and Aétosauria, by the appearance
of a supratemporal fossa, which develops between parietal,
squamosal, and the upper posterior border of the orbit. The
bony arch below the supratemporal fossa which connects the
orbit with the quadrate is now affected in two different ways:

No. 3.] VERTEBRATE-SKULL. 473

1. The broad single arch remains single, but becomes more
and more slender and can be interrupted. Plesiosauria,
Theromora, Mammalia, Squamata (Lacertilia, Pythonomorpha,
Ophidia).

2. In the broad single arch appears another opening, the
infratemporal fossa forming an upper and lower arch which
connects the orbit with the quadrate: Rhynchocephalia, the
whole archosaurian branch (Crocodilia, Dinosauria, Pterosauria), .
Birds.

Until now the Squamata had been considered by a large
number of anatomists as derived from the Rhynchocephalia,
and I have held the same view. The Squamata were looked at
as Reptiles, in which the lower temporal arch of the Rhyncho-
cephalia had disappeared. But this is not the case. It seems
very much more probable that the Squamata never possessed an
infratemporal fossa, but that the broad arch was reduced from
below in the same way as in the Testudinata ; and that the old
opinion of Hallmann, Hollard, Owen, that the squamosal of the
Squamata is the homologue of the quadratojugal, and the supra-
temporal or mastoid of the Squamata the homologue of the
squamosal of the Archosaurian branch, is the correct one. In
all Reptilia, if no reduction has taken place, there are two
elements between quadrate and parietal: the only exception is
found in the Ichthyosauria. In these a third bone is inserted,
which has to be considered as an original part of the upper
bone. The same element is found in the Stegocephalia. In all
these forms in which a quadratojugal has been recognized, there
is never a “supratemporal” (as seen in the Lacertilia) ; in all
forms in which this supratemporal was found, there is no quad-
ratojugal. From a careful comparison of the skulls of the
different groups of Reptilia, I reach the conclusion that the
supratemporal or mastoid (opisthotic, Cope) of the Squamata
is in fact the squamosal, and the bone called squamosal the
quadratojugal.

In the Iguanida, Agamidze, Lacertide, Anguidz, Varanide,
both bones are well developed; in the Helodermatidz the
squamosal (supratemporal, Parker; opisthotic, Cope) is large,
the quadratojugal (squamosal, Parker) very small; in the Ophidia
the quadratojugal has disappeared entirely. In the Tejidz the
squamosal becomes reduced and united in some forms with the

474 BAUR. [Vot. III.

quadratojugal. In the Geckonidz generally only one bone is
present ; this represents the quadratojugal, the squamosal may
be lost entirely or reduced to a diminutive scale. In the Cha-
mzeleontide the quadratojugal has been greatly enlarged at the
expense of the squamosal, which has been almost entirely re-
duced. In the Rhynchocephalia (Sphenodontidz) and Chamee-
leontidz we have the two extremes of development of these two
elements. In Sphenodon the squamosal is very large, the quad-
ratojugal very small; in Chameleon, the quadratojugal is very
large, the squamosal very small.

In the Plesiosauria, Theromora, and Mammalia, the quadrato-
jugal and squamosal are confluent with the quadrate.

Sept. 15, 1889.

ON .THE .POSELMON, OF .€CRAIL7 A AN THE
SYSTEM.

R. W. SHUFELDT.

THERE are two species of Chama in the United States avi-
fauna, — the C. fasczata, which is confined to the coast region of
California, and C. f. henshawt, a variety of the latter which
ranges through the “ interior of California, including the western
slope of the Sierra Nevada.” Ornithologists have bestowed the
name of the Wren-Tit upon the first-mentioned of these, while
the second one is referred to as the Pallid Wren-Tit. In the
absence of any detailed and published account of the structure
of Cham@a, made comparative with its supposed affines, one
would naturally be led to believe, from these names, that the
systematists regard these birds as Tits with a tincture of Wren
in them ; and such, I understand, is generally the case, or other-
wise they would certainly have been designated as Tit-Wrens.
Several dissenters from this opinion are, however, known to me,
and chief among these I would allude to Mr. Robert Ridgway,
Mr. I. A, Lucas, and Mr. J..A. Allenay in conversation with
Mr. Ridgway on the subject, although he seemed to be dis-
inclined to advance any decided opinion in the premises, he left
the impression upon my mind that he regarded Chame@a more as
a Wren than a Tit, and very kindly allowed me to examine skins
of both groups in the collections of the Smithsonian Institution.
Among these he was so good as to point out and invite my
attention to the external characters in such forms as Czznicer-
thia untbrunnea and Cinuticerthia unirufa, the first being a spe-
cies from Ecuador, and the latter from Colombia. He remarked
that, in his opinion, these birds were Wrens, and I was struck
with their general: external resemblance to Chamc@a, more
especially in the case of wxzrufa, which, if I remember, was the
species with the longer tail. Both, however, were, upon the
whole, unitinted ; their heads tufti-crested; a tendency in one
for the tarsal scutella to become obsolete ; and in the case with

476 SHUFELDT. [Vor. III.

both, the form, size, bill, and general faczes were considerably
like Chamea. It was also interesting to note that these birds
had the flight-feathers of the wings indistinctly barred, as we
so often find them among certain troglodytine types.

Mr. Lucas has published it as his opinion “that Chamea
appears most decidedly to belong with the Wrens, and not with
the Titmice.” (voc. 7. S. Nai Mus., 1888; p. veo) imally,
Mr. J. A. Allen, in a letter to the writer under date of June 14,
1880, says, “I know of no South American forms near Chamea,
outside of the Wrens, of which South America furnishes a large
and varied assortment.”

With these facts before us, it would seem that a careful com-
parative study of the structure of Chama could be nothing less
than a well-chosen task, and one decidedly worthy of the labor
required to complete it. It is such a work that I have to present
in the present paper, and I am indebted to a number of my
friends for material wherewith to prosecute it. Chief among
these it gives me pleasure to thank Mr. F. Stephens, of Ballena,
California, for upwards of a dozen specimens of Chamea fasciata
henshawt, and adult and young of Yhryothorus 6. spilurus ; this
material was collected for me by Mr. Stephens, and generously
donated by Mr. G. Frean Morcum, of Chicago. They were all
alcoholics. Ten or twelve years ago I also received a good
skeleton of Chamea fasciata from Mr. C. A. Allen, of Nicasio,
California, and my thanks are due to the same naturalist for a
specimen of Parus rufescens in alcohol. Mr. Herbert Brown, of
Tucson, Arizona, sent me a series of beautiful specimens of
Auriparus flaviceps and Campylorhynchus brunneicapillus, which
yielded some excellent skeletons, for which I was especially
grateful. My valued friend, Professor Alfred Newton, F.R.S.,
of Cambridge, England, generously sent me alcoholics of adult
g and 9, and juv. of Accentor modularis, which were suggested by
him to be compared in the same connection. It was also through
Professor Newton’s kindness that I obtained from his friend,
Lieutenant W. Wilfrid Cordeaux, of the 2d Dragoon Guards
(Queen’s Bays), some fine alcoholic specimens of the Paride
of the Northwestern Himalayas. Still later I was favored by
Dr. George Bird Grinnell with a specimen of Pertsoreus canaden-
sts capitalis, with which I intended to make some comparisons of
the skeleton between it and representatives of the sub-genus

No. 3.] POSITION OF CHAMAA. 477

Lophophanes among the Titmice. Lieutenant Cordeaux kindly
made the collection especially for the present work in the
region indicated, and Dr. Leonard Stejneger did me the service
of identifying the specimens after they came into my hands.
Dr. Grinnell secured the Jay, to which I have just alluded, in
Wyoming, and my thanks are due him for his thoughtfulness in
the matter. Finally, Iam much indebted to Mr. H. K. Coale,
of Chicago, for numerous alcoholic specimens of North Ameri-
can Tits and Wrens sent me at different times to be used in the
present memoir. My own collection affords either alcoholic
specimens or skeletal preparations of an extended variety of our
United States Paride, Certhiide, Cinclide, Troglodytide, and
Mniotiltide, which I have collected during the past fifteen years
in widely separated parts of the country.

From the material at hand it will be seen, then, that the
principal forms that we lack for comparison are the various
species of Wrens of the South American avifauna spoken of
by Mr. Allen in his letter, and no one can regret more than the
writer the absence for such a purpose of such species as are to
be found in the genus C7zznzcerthia, to which we have already
alluded. But as those birds have never as yet been carefully
examined and compared structurally with the species to be thus
dealt with in this paper, we are just as likely to find them to be
Wren-like Tits, a little nearer the Wrens than Chamea, as any-
thing I know anything about. In its topographical characters
Cinnicerthia unirufa, to be sure, very much resembles Chamea
fasciata, indeed very much more so than do either one of them
resemble any of our North American Wrens.

Not long ago Mr. Sharpe described a new species of Czzuz7-
certhia, in the Catalogue of the British Museum, I think, that
looks from the drawing still more Wren-like than the two species
alluded to in the previous paragraph, it possessing a longer bill
and being still more distinctly barred on the wings and tail.
Dr. Sclater in his NMomenclator Avium Nectropicalium places
the Ciunicerthia among the Wrens, and next before the genus
Campylorhynchus ; and a number of ornithologists are of the
opinion that our genus Z7hryothorus is the most nearly related
genus of Wrens to C7zuxnicerthia, — that is, in the United States
avifauna.

Among the typical Tits, so far as I have examined them, we

478 SHUFELDT. [Vot. III.

find no species that particularly resembles Chamea in its gen-
eral appearance. A mounted specimen of the Bearded Tit, in
the collections of the Smithsonian Institution, which was shown
me by Mr. Robert Ridgway, has some external characters, both
in general form and less so in color, that suggest to our mind
an affinity with perhaps some such form as our Chame@a. Be-
yond it, I found no species that appeared to offer any clue.

However, as I said before, if we confine ourselves strictly to
the United States avifauna in the comparisons we make with
Chamea, 1 am strongly inclined to believe that in the entirety of
its structure it will possess more parine rather than troglodytine
characters in its organization. For instance, when we come to
consider a// the external characters of Chamea, its habits, its
nest and eggs, its habitat, and other matters bearing upon its
history as a species, — taking all these, I say, into careful con-
sideration, and without any regard to its internal structure, and
even setting aside for the present its pterylography, I see its
nearest allies in the various species of Psaltriparus, and sec-
ondly, in some very few particulars, in the sub-genus Lopho-
phanes among the Paride. In point of size and in the tufted
feathers of the head it more nearly resembles the last-named ;
while in habit, and in its rounded wings and long, graduated tail,
and other points, it comes closer to species in the first-mentioned
genus. Its resemblance to such a species as Auriparus flavt-
ceps is, of course, very slight, and indeed that somewhat highly
colored little bird is the most un-Tit-like-looking Tit that has
been allowed a place among our United States Paride.

In the subjoined TaBLE I contrast a few of the characters,
etc., which characterize the subject of this memoir and such
other species and genera as Psaltriparus, Auriparus flaviceps,
Parus, Accentor, and Thryothorus. When Professor Newton
sent me the specimens of Accentor modularis to compare with
Chamea, he was, I think, more especially impressed with the
fact that both the birds laid 4/we eggs, and in both the habits
are not altogether unlike. As our examinations into the struc-
ture of these forms progress, however, I am convinced that Ac-
centor will prove to be a form very much like some of our larger
American Warblers, such as for instance Geothlypis macgitlt-
vrayt, or perhaps some other. I have examined, through the

POSITION OF CHAMEA. 479

No. 3.]

SPECIES AND GENERA, GENERAL ForM.

Tit-like rather
than Wren-like.

Chamea fasciata.

Very small spe-

Psaltriparus (the genus). diese. Tits
; i

Auriparus flaviceps. Sylvicoline.

Parus (N. Amer. forms of

the genus), Strictly parine.

Sylvicoline chief-
ly.

Accentor modularts.

Thryothorus (N. Amer.

Compact ; typical
forms of the genus).

Wrens.

TABLE.

CHARACTER OF PLU-
MAGE.

Soft and lax.

Soft and lax; tail
long as in Chamea.

Compact ; not es-
pecially soft.

Loose, long and
very soft, may be
crested or the reverse.

Not
compact.

particularly

Very compact;
heads not crested ;
tail short.

PREVAILING COLORS
IN PLUMAGE, ETc.

Various shades of

Ashy-gray, paler
below, not crested.

Head yellow; red
in wings; general
color ashy.

Black, gray, and
white; tail may be
long or short.

Brown; head not
crested; tail rather
long.

Brown; various
shades. Shows mark-
ings.

TARSUS AND OTHER
POINTS.

Obsoletely scutel-
late; iris white.

Distinctly scutel-
late; iris yellow or
brown.

Ditto. Tail short;
head not crested.

Distinctly scutel-
late; iris dark.

Distinctly scutel-

late,

Scutellate. | Nos-
trils exposed, not

feathered over as in
Tits.

NEst, Eccs, AND
REMARKS.

Nest in bushes;
eggs plain greenish
blue (Coues).

Nest pensile, large,
side-opening ; eggs
6-9, plain white.

Nest globular; eggs
spotted and white.

Nest excavated;
eggs 6-9, white, and
spotted.

Nest in bushes;
eggs 6, blue.

Nest built in any
suitable nook or re-
ceptacle; eggs white
and spotted.

480 SHUFELDT. [Vor. III.

courtesy of Mr. Ridgway, skins of both A. modularis and A. vul-
garis, and this recent examination has in no way altered the
opinion I expressed on this point a year or more ago; indeed, it
has in fact only strengthened it. So far as its topographical
anatomy goes, A. modularis has all the appearance of a large
ground Warbler; still, I intend to carry it along in our examina-
tions in the present monograph, as it will widen the field and
prove useful in other ways.

Of the Pterylography. — Upon plucking a specimen of Cha-
mca, the ornithotomist is at once struck with the great length
of the thighs and legs as compared with the size of the body of
the bird. Further, it becomes evident that the pectoral limbs
are relatively short, a short brachium, antibrachium, and pinion,
and likewise this species has a short, thickset neck. As we
would naturally expect, we find the pattern of the pterylo-
graphic areas to be passerine, with the “saddle tract” of the
spinal pteryla to be rather small and distinctly lozenge-shaped.
The continuation of this from its posterior angle to the uro-
pygial (and untufted) gland is composed of almost a single line of
feathers. The “ventral tracts” seem to present nothing peculiar.

After removing the plumage of a specimen of Parus inornatius
griseus, it is seen to markedly differ in form from Chamea, be-
ing indeed in contour the perfect miniature of a Jay in this par-
ticular; and this species may remotely link the Paridé and the
Corvide, perhaps through such a genus as Perisoreus. As to
its pterylography, we find the “ventral tracts’’ considerably
broader in proportion than they exist in Cham@a, while the
“saddle” of the spinal tract is more inclined to be rounded at
its corners, though the same meagre line of feathers is con-
tinued from it below to the tail. There is a great deal to be
learned by the careful study and comparison of the plucked
bodies of birds, and similarity of form should be given its due
weight. I was never more thoroughly impressed with this fact
than when I for the first time compared the plucked bodies of
a Swift and a Humming-bird. No two birds could be more
thoroughly dissimilar than these in this important particular.
Parus tnornatus griseus has the “alar tracts” very densely
feathered, and in this species there is an evident tendency for
the tracts of the shoulders and neck to run together, — not so,
however, in the subject of our paper.

No. 3-] POSITION OF CHAMAA. 481

Serving a specimen of Psaltriparus plumbeus, as in the fore-
going specimens, we at once recognize how very much it agrees
in form with Chamea, and how it differs from Parus tnornatus
griseus. Once more we find the disproportionately long thighs
and legs, with the short, thickset neck, though in Psadtriparus
the pectoral limbs are relatively larger with respect to the size
of the body than they are in Chamea.

The pattern of the several pterylographical tracts are almost
identically the same in these two genera.

With respect to form and pterylography the Chickadees, as
represented by Parus gamdbclt, seem to offer the precise inter-
mediates between Chame@a and P. 2. griseus (Lophophanes), or
between Psaltriparus and the latter. For in them we find a
harmonious balance between limbs and body, though the pelvic
pair are rather long. The neck is proportionately longer, and
the head moderately smaller. Indeed, one might say in the
body of this Chickadee there are really no proportional discrep-
ancies, any more than there are in the form of the body in an
average Sparrow. This mountain Chickadee likewise shows
some departure in its pterylography, for the ventral tracts are
much narrowed ; the saddle of the spinal tract lozenge-shaped
again, while quite a broad band of feathers, several rows at
least, connect this latter with the dorsal caudal pteryla. All the
Tits I have thus far plucked have the skin of the head, with the
exception of that covering the throat, of a dark purplish hue;
and I am inclined to think that this is normal with them.

At some other time the writer has it in his mind to give the
anatomy of the genus Sz¢fa ; and as there can be no very inti-
mate affinity between it and Chamea, we will not take it into
consideration here. This should not debar us from taking a
glance at such a form as Regulus satrapa, and I am under obli-
gations to Mr. H. K. Coale of Chicago for alcoholic specimens
of this species. After one has been carefully plucked its diminu-
tive body calls up to us Psaltriparus, but not so its form ; for
in Regulus we have the true sylvicoline contour, with its far
more acutely conical head, the deep-set eyes, the justly propor-
tioned limbs for the size of the body, which latter is robust,
broad, showing evidences in front of the more prominent keel
of the sternum.

Regulus has a large, lozenge-shaped saddle in its spinal tract ;

482 SHUFELDT. [Vot. III.

and this pteryla is quite broad, as it is continued on to the tail,
the whole system of the pterylography causing the feathering
to be quite dense in this species.

Both the form of the body and its pterylography in Regulus
is substantially repeated in Polzoptila plumbea, a specimen of
which species I have this moment plucked, and now have before
me. In it, however, there is an evident arrangement of the
feathers in the capital area; for a strong, single, median row
can be easily recognized, and another single row passes over
each eye. The median row bifurcates anteriorly, the base of
the culmen passing between the limbs, which latter have on
either side the lateral orbital row merging into it. Judging from
form of body and pterylography alone, I would hardly say there
was any very close affinity between Chame@a and the last two
genera we have examined.

In the lot of alcoholics kindly collected for me by Mr. Coale,
I also find an excellent specimen of Certhia famtliaris amert-
cana; but aside from its curved and slender beak, the form of
the body of this species is sylvicoline, with troglodytine affini-
ties quite pronounced, while its pterylography is strictly pas-
serine. From its topographical anatomy, and what we know of
its habits, it surely has but a very slender kinship with Chamea.

The pterylography of Certhza familiaris has been correctly
figured by Nitzsch.}

Passing next to one of our specimens of Accentor modularis,
I find upon plucking it that its pterylography is very different
from Chamea, having quite the same pattern which Nitzsch
figures for Motacilla alba,? though in Accentor the saddle tract
of the dorsum is if anything proportionately larger, and the
pteryla leading from it to the uropygial gland broad, and spread-
ing posteriorly at its termination. All the pteryle are clearly
defined and strong in the Accentor.

The form of the body in this bird is what one might suppose
to be as across between one of our average Sparrows and a large
Warbler, say for instance, D. vigorsiz x Ammodromus, at once
noticeably different in contour from the subject of our paper.
An arrangement of the feathers on the top of the head in this
species are as I described them for Polopizla, with the exception

1 Prerylography, Eng. ed. by Sclater, Taf. III., fig. 3.
2 Jbid., Taf. IIL., figs. 1 and 2.

No. 3.] POSITION OF CHAMAA. 483

that the median band is much broader. And I wish it to be
understood that in both species scattered feathers are to be
found interspersed among the three longitudinal bands which I
have attempted to describe. This condition is also pretty well
seen in Cham@a. There is but one other species we will exam-
ine just at present, so far as its topographical anatomy goes ;
and I propose to allow Sa/pinctes obsoletus to represent the
Wrens, it being a good-sized Western form. In it we find a
pterylography which approaches Certhza more nearly than any
other species we have investigated, while in the form of its
plucked body, it widely departs from Chamea, as its head is
conspicuously large for its size; the neck rather long; the body
or trunk very wide and compressed dorso-ventrally ; the pectoral
limbs long and powerfully developed ; and finally, the pelvic
extremities relatively short, and not especially strong. Chamcea
Jasciata has very little affinity with this bird, so far as is indi-
cated by external features and characters; and these are as
much a part of its anatomy as are brain, viscera, or skull. The
form of the plucked body in Salpznctes obsoletus is substantially
repeated in Campylorhynchus brunnetcapillus.

To sum up a little, then, as far as we have gone, and spread-
ing out before us all our specimens of plucked birds now under
consideration, carefully reweighing everything that has been set
forth in the foregoing paragraphs, —then by a system of elim-
ination, putting first aside the species having the greatest num-
ber of different characters, then the next one most evidently
unlike our Chamca, we find at last that we are compelled to
decide in favor of a Psaltriparus as having the majority of
characters in its external parts that approach the subject of our
present memotr.

Turning for the moment to such foreign forms as 4/gzthaliscus
erythrocephalus, Parus nepalensts, and Parus xanthogenys from
the northwestern Himalayas, we find some interesting compara-
tive points in them; for in the first-named species the general
form of the plucked bird quite nearly resembles Chamea and the
Bush-Tits of the genus Psa/triparus, in that its pterylography
is very much the same; while the shape of the head, the shortish
neck, and the lengthening of the pelvic limbs, though the latter
is not so striking, all point toa parine structure, which approaches
our Wren-Tit.

484 SHUFELDT. [Vot. III.

This, however, does not apply to the two last-mentioned spe-
cies, for in them these characters are far more like what we
find in some of our typical Titmice, more especially such species
as Parus gambeli or Parus atricapillus and its varieties.

I would also especially note that the shape of the bill in
A. erythrocephalus more nearly approaches that part of the
anatomy in Chame@a than any other bird which I have compared
with it, or which is supposed to bear any relationship with it.
Let us next cut down upon some of the internal structures, and
see what they seem to point to, in the way of affinities.

The lower larynx or syrinx in Chamea, both in structure and -
its musculature, seems to depart in no way whatever from its
constitution in the smaller passerine birds generally. I have
examined it in a number of species, including Accentor and the
Paride.

The ¢ongue, agreeing in its principal features with the tongue
in true passerine birds, has, nevertheless, its extremity in Cha-
mea bluntly truncated square across, and this margin finished
off with a fringe of fine fimbriations. This is the case in most
of the Tits, while in the Wrens (Sa/pzuctes) the extremity of the
tongue seems to be simply pointed, and in Accentor it is dis-
tinctly once notched in the middle line, with the bifurcations
showing a tendency to fringe.

As usual in Passeres the left carotid artery is the only one
present, not only in our subject, but in all others examined.

Upon examining the zx¢estinal tract, we find the pair of small
coeca present in all the species under consideration, and Chamea
agrees with both Wrens and Tits in possessing a wonderfully
small gizzard. And in these birds the organ consists of a
strong, firm internal corneous coat, overlaid by a thin and
delicate muscular one which readily peels off, leaving the com-
plete corrugated cast of the dense internal layer. This is the
case also in the Himalayan Tits referred to above. <Accentor
modularis, on the other hand, has a conspicuously large gizzard
of very different structure ; for although it has a small corneous
internal coat, this latter is covered by a thick and strong mus-
cular layer, and upon opening it I find numerous pieces of hard,
flinty gravel (as large as No. 8 shot) mixed with seeds and in-
sects. Measuring the greatest median longitudinal line of the
plucked head of a specimen of Chame@a, we find it to be equal

No. 3.] POSITION OF CHAMAA. 485

to 3.2 cms., while the greatest diameter of its stomach in any
direction is equal to 1.2 cms. Now the same measurements for
the following species are : —

Head Stomach
farus inornatus griseus sia jas ve) «352, CMS.) 1.1) CMs.
ALCENTOT MUMULEFES coe so lihas al anne eeu aE tee Boe a
DSTIPINGIES ODSOULLYES. ia ru) eu ti eta) te PSO o 1
PSAUPDEVUS DIETIOCUS Mn 3), tah | ie too) 0.9 '*

Further, I would add that the corneous layer of the gizzard
in Accentor is much thinner than we find it in the Wrens and
Tits, while the external form of the organ is entirely different.

Having carefully examined the myology of the limbs in Cha-
mea and compared it with the corresponding structures in Tits,
Wrens, Warblers, and the Accentor and others supposed to be
more or less nearly related to our subject, I find no essential
differences that will aid us in determining affinities. In all
these forms, so far as I have been enabled to discover, the ori-
gin and insertion of the patagial muscles of the arm and the
thigh muscles are essentially passerine.

With these investigations of the “soft parts” of Chamaa
and its supposed affines before us, we will next pass to a
comparative consideration of its skeleton.

OF THE OSTEOLOGY.

The Skull. — A great many of our smaller and ordinary pas-
serine birds, such as the Wrens, Warblers, and some few others,
have the superior osseous mandible, and the large subelliptical
narial aperture on either side of it, constructed very much upon
the same plan. The culmen is more or less curved gradually
from frontal region to apex; the lateral edges are cultrate ; and
there is never any bony septum nasi, while it is entirely open
on the under side between the delicate anterior limbs of the
palatines. Seen upon side view, this pattern of the upper
bony beak is well shown in Chamea or in Psaltriparus or in
Regulus (Figs. 1, 3, and 4), while, though the plan remains
identically the same, the form is somewhat altered by the
lengthening of the beak in such Wrens as Sa/pinctes (Fig. 7),
Thyrothorus 6. spiturus, and the Canon Wren (Catherpes). It
is seen again in the Warblers, where recognizable differences of
form obtain to an extent in this part of the skull sufficient to

486 SHUFELDT. (VoL. Ill.

allow us to distinguish between the genera in some cases — not
always an easy matter. For instance, in the numerous skulls
of Warblers before me, the superior osseous mandible of Den-
dreca estiva is markedly more like Chamea in this particular
than is the Prothonotary (Protonotaria), and Mnzoiilia more
than either.

In this particular Psaltriparus plumbeus (Fig. 3) is most like
Chamea ; Accentor agrees better with some of our M/nzotdtide ;
while a departure becomes evident as we pass to certain Titmice.

Figure 1.— Chamea fasciata.
Figure 2.— Accentor modularis.
figure 3.— Psaltriparus plumbeus.
Figure 4.— Regulus satrapa.
Figure 5.— Parus | Lophophanes] tnornatus griseus.
Figure 6.— Parus gambeli.
Figure 7.— Salpinctes obsoletus.
Figure 8.— Certhia familiaris americana.
These figures are all right lateral views, and life size, by the author, from the
specimens.

No. 3.] POSITION OF CHAMAZA. 487

This change begins to be apparent in the Chickadees, as in
Parus gambelt, or in the skull of P. carolinensis of a specimen
kindly presented me by Mr. Coale, or in P. rufescens. It con-
sists mainly in a decrease in the size of the openings of the
nostrils, and a broadening of the culmenar bridge between
them. And it is in such species as Parus tnornatus (of the
subgenus Lophophanes) that we find a vastly different state of
affairs prevailing (Fig. 5), for in them the upper bony beak is
shorter ; less pointed anteriorly ; broadly rounded from side to
side for the entire length of the culmen; the narial apertures
subcircular instead of subelliptical in outline; their superior
arcs widely separated by the great width of the nasal processes
of the premaxillary. Viewing the skull upon its superior aspect,
we find that in Chamea the frontal region is extremely narrow
between the upper edges of the orbits, more so, in comparison
with its size, than in any other species we have under consider-
ation, although the feature is common to them all. The cranial
vault, the sides and back of the brain-case included, is a smooth
and rounded dome in Chamea, the Wrens, Tits, Accentor, Regu-
fus, and the rest, though it differs in the various genera and
species, both in form and relative extent. For the size of the
bird, Chamea has decidedly the largest cranial capacity, Psaltri-
parus about equalling it in proportion to its size, followed by
Parus tnornatus, then Regulus and the Chickadees; while the
Wrens have a small brain-case as compared with their size, the
same applying to Accentor and our Warblers. Lophophanes has
the posterior moiety of either orbital rim raised all round, a
feature less marked in the Chickadees, while in Chamcea, the
Bush-Tits, and Wrens it does not exist.

Some good distinguishing characters are also to be found on
a lateral aspect of the skull, more especially in the condition of
the interorbital septum. Barely any bone is to be found here
at all in Chamea, it being absorbed by a large vacuity occupy-
ing the central part of the partition, separated only by a slender
bar from the great coalesced openings above where issue the
first pair of nerves. The optic foramina have also merged, and
it consists now in a small, central, circular foramen completely
surrounded by bone, at the median point of the upper arc of
which the posterior end of the extremely delicate osseous rod
which bounds the interorbital vacuity above is attached. Psal-

488 SHUFELDT. [Vot. III.

triparvus and most Wrens repeat this state of affairs almost
exactly (compare Figs. 1, 3, and 7), while the septum is more
nearly complete in Accentor, while in the Tits, more especially
in Lophophanes, it comes very near being entirely so (Figs. 5
and 6). The zygoma is reduced to almost hair-like dimensions
in all of these species, and the pars plana separating the orbital
and rhinal spaces is comparatively large, tumorous, and of a
quadrilateral form. Few characters, if any, are afforded by the
posterior aspect of these skulls; in all this part of the cranium
is rounded, quite smooth, always shows a supraoccipital promi-
nence, but never the foramina on either side of it. So well
known is the arrangement of the palatal osseous structures at
the base of the skull in these ordinary passeres, that we will
refrain from entering upon a detailed description of them here.
The various parts, more particularly the palatines and maxillo-
palatines, differ to some extent in form in the several genera
and species, but the arrangement remains essentially always the
same. In all except Lophophanes the vomer is truncated an-
teriorly and variously notched, while in the excepted genus this
bone shows a longitudinal median carination beneath, and is
carried, in the specimen before me, to a point in front, as a
whole it being shaped something like a diminutive oblanceolate
leaf. Psaltriparus plumbeus has the bony structures at the
-base of the skull most like the corresponding ones in Chame@a ;
the Wrens and Chickadees seem to stand next in this regard,
Accentor approaching the. Muizotiltide. Generally the narial
ends of the maxillo-palatines are dilated into a small paddle-
shaped extremity, but in such a form as Regulus satrapa, how-
ever, no such enlargement exists, these processes each being
long and very slender. Normally, they are not in contact either
with each other or with any of the surrounding bones, and the
_ vomer fuses with the palatines behind.

Of no very great strength in any of the species before me, the
mandible in all is of a V-shape form, and differs principally in
the size of the ramal vacuity. This is very large, relatively, in
Chamea, Psaltriparus, Crested Tits, Chickadees, and some
others, but notably diminished in size in most Wrens, where it
may disappear altogether in some species.

Nothing worthy of special note characterizes the hyoidean
apparatus, still less the intrinsic ossifications of either the eye or

No. 3-] POSITION OF CHAMEA. 489

ear, their structure in these passerine types being well known,
as is the fact that they seldom, if ever, offer us any important
characters upon which to assist us in determining affinities.

Of the Remainder of the Axial Skeleton. — There are nineteen
free vertebra between the skull and the pelvis in the spinal col-
umn of Chamea fasctata, and of these the first eleven are
without ribs; the twelfth supports an exceedingly minute pair
of rudimentary riblets; on the thirteenth these are longer; on the
fourteenth they are fully developed, and have uncinate processes,
but do not reach the sternum. The next five vertebra bear
complete ribs, which connect with the sternum by hamapophy-
ses, and the thoracic ones all have long slender uncinate
processes ; finally, there is a pair of “ sacral ribs,” without these
latter, and whose hzemapophyses fail to reach the costal border
on either side of the sternum.

Psaltriparus plumbeus agrees thus far, with respect to the
vertebrae and ribs between skull and pelvis, with Chamea, and
in both species the ribs in particular are very delicate structures ;
in the Bush-Tit being fully as much so as the ribs in a skeleton
of the Rivoli Humming-bird (Eugenes fulgens), for which I am
indebted to Mr. W. W. Price, of Tombstone, Arizona, who
recently collected the specimen near that place, and presented it
to me.

We also find, in this part of the spinal column, nineteen verte-
brze in Accentor, but this species differs in this, that the hama-
pophyses of the last dorsal vertebrz do not arrive at the costal
borders of the sternum. This arrangement disagrees even with
our North American Warblers (Compsothlypis, Dendrotca, Pro-
tonotaria, and several others), and just at this moment I fail to
recall to mind the sternum of any ordinary small passerine bird,
that has, as have the two sterna of Accentor modularis before me,
but fowr hemapophysial facets upon either costal border. I
pointed out several years ago that in Otocorzs the first pair, or
one of the first pair, on either side, of the hamapophyses, may
fail to be present, and thus have a sternum with only four
facets on either border, but in Accentor the missing facet is at
the other end of the row. (Contributions to the Anatomy of
Birds: Ostcology of Eremophita.)

The ultimate hamapophyses in Accentor barely clear the cos-
tal borders of the sternum, and it is just possible that speci-

490 SHUFELDT. PVon. TM.

mens may be found wherein their lower ends make their impress
on the lateral sternal margins.

In a specimen of Parkman’s Wren, which I collected here at
Fort Wingate, New Mexico, in 1885, there are also nineteen
vertebree in the column, between skull and pelvis, with the
same arrangement of the ribs as in Chamea, but the twelfth ver-
tebra, although the vertebral canal on either side of it is not
closed, its pleurapophyses have not either been liberated as a
pair of tiny ribs. This may prove to be the case in the majority
of specimens of Chamea, but it is a matter of minor importance,

Among the Titmice (Parus) the same arrangement of the
vertebre and their ribs obtains in this, the cervico-dorsal division
of the column, and I am inclined to believe it to be characteris-
tic of the majority of groups of oscine birds; S/wrnella, the
Orioles, and some of the Crow-Blackbirds forming the principal
exceptions. (See author’s “The Skeleton in the Genus Stur-
nella,” etc., Fournal of Anatomy, London, April, 1888, Vol.
XXII.) The comparison of this part of the skeleton then, in
Chame@a and its supposed affines, will not assist us much as a
diagnosis of possible kinships among the various species under
consideration, so we will next take a look at the pelvis.

Chamea has a pelvis fashioned after the general passerine
type or model, and its sacrum, or the number of vertebrze that
have co-ossified with it, seem to be twelve. This part is very
large, as may be seen by examining it upon its ventral aspect,
where a longitudinally disposed parial row of quadrilateral pit-
lets mark it for nearly its entire length. The obturator space
is very large, while the hinder ends of the post-pubis and ischium
on either side flare outwards a good deal. Proportionately, the
ischiadic foramen is also big, and the obturator foramen com-
pletely surrounded by bone. Viewing this pelvis from above,
we note that the praeacetabular portion is narrow, and the ilia
much concaved, the fore part of the internal margins of these
bones not meeting here, but they gradually approach each other,
and are finally in contact in the middle line, at a point just a
little anterior to an imaginary line joining the acetabule. The
post-acetabular space is broad, and of a quadrilateral outline.
More or fewer pairs of interdiapophysial foramina are here seen,
disposed as usual in a double row.

Of all the pelves before me, none approach, in detail, this pel-

No. 3.] POSITION OF CHAMAA. 491

vis of Chame@a, so closely as does the pelvis of Psaltriparus
plumbeus, in which species this bone is quite the miniature of
our subject’s. One point, however, must be noted, and in the
Psaltriparus the ilia do not come quite in contact on the dorsal
aspect, as we have stated above to be the case in Chamea.

Passing to the Crested Tits (Lophophanes), the pelvis still
bears the same general features, but in it the internal margins
of the ilia, opposite the acetabule, are yet further separated, and
the sacrum here upon the dorsal aspect thoroughly exposed,
in consequence, for its entire length.

Chickadees and Wrens are in the same case, their pelves
agreeing very well with the others described, and with the
sacrum well in sight along its entire dorsal aspect, the ilia not
meeting each other in any part of that locality.

Accentor has a very different pelvis from this; and it agrees
best with that bone in some of our larger Mniotiltide, with a
trace of the Sparrow in it, and belongs to a bird quite thoroughly
removed from Chamea.

Counting the free caudal vertebre in our subject, I find there
are szx of thent, not including the large pygostyle. This latter
bone has here rather a peculiar shape, its superior laminar por-
tion showing near its centre an area where the bone is much
thinner than at the edges; while below it is somewhat spread
out, after the fashion of the Pzcz, only in a far less degree.

Six plus a pygostyle is also the normal complement in Psa/
triparus and all other Tits examined, as well as in the Wrens,
and in Accenzor, and finally in such species as Polioptila plumbea,
Regulus, and Protonotaria citrea. Let us next take a glance at
the bones of the shoulder girdle in these several groups of birds ;
and first, in Chamcea, we find the os furcula to assume the broad
and deep U-shape pattern, its limbs being reduced to almost °
capillary dimensions, with a mere apology below for a hypo-
cleidium, while the coracoidal ends of the limbs are compara-
tively very much expanded. A scapula has a long, narrow, thin
blade, the posterior third of which is turned considerably out-
wards, and its apex carried to a fine point. Most interesting,
however, of all three is a coracoid, which here attains to a won-
derful length, the bone being not a little longer than the greatest
longitudinal diameter of the body of the sternum (not including
the manubrium in the measurement). Its shaft is subcylindrical

492 SHUFELDT. [VoL. III.

=<

and straight, with its sternal end only moderately expanded, as
is the other extremity of the bone, only moderately tuberous.
When articulated zz sztu, these bones show no marked departures
from the corresponding arrangement in all ordinary oscines.
The Bush-Tits (Psaliriparus) have the bones of the shoulder
girdle in all respects very similar to those just described for
Chamea, not omitting the unusual length of the coracoids, which
here lack but little of being fully as long as the entire sternum.

In Lophophancs the hypocleidium of the os furcula is inclined
to be slightly more prominent ; but beyond this minor difference,
little change is to be discovered in the elements of this pectoral
arch, beyond what has been given above.

Troglodytes among the Wrens may have the furcular hypoclei-
dium still more conspicuous, and this also applies to the genus
Salpinctes. Os furcula among these latter birds still retains its
frail structure, a broad U in form, gently curved backwards for
its inferior moiety, which curvature begins almost imperceptibly
near its middle.

When we get among the skeletons of the Warblers (A/xzo¢z/-
tide), little change is to be found in the shoulder girdle; but
with them the hypocleidium of the fourchette is always of good
size, as it is in Accentor modularis.

Chamea fasciata has a sternum of the well-known passerine
pattern. It is peculiar, however, in that it is strikingly flat,
there being but little concavity apparent upon its thoracic
aspect. Its outer xiphoidal processes are wonderfully slender,
and the midportion very broad behind, which latter fact renders
the outline of the body quite square. Its keel is shallow and
weak. Indeed, the entire bone in this bird is a very delicate
one, as compared with the size of its owner. Psaltriparus plum-
bcus has a sternum the very counterpart of the bone in Chamaa,
only in miniature. Its body, however, is more concaved, and the
mid-xiphoidal margin not so long comparatively. Its pattern is
considerably changed in the Crested Tits (Lophophanes), where
the body is far more oblong rather than square; the mid-
xiphoidal margin much more contracted; the ‘notching,’ com-
paratively speaking, not so profound as in the Bush-Tits; the
keel more ample; and the costal processes and manubrium
strongly developed. The latter shows a deep carination be-
neath, which is scarcely at all evident in Chamea. Troglodytine,

No. 3.] POSITION OF CHAMAA. 493

although they have, asa rule, a sternum in each species with a
style to it of their own, yet by the slightest modification it could
be easily made to assume the pattern of the bone, as we find it
among most North American Paving. For example, how much
the bone is alike in two such species as Salpznctes obsoletus and
Parus tnornatus ! Again, take three such sterna as are offered
us in the skeletons of Pyrotonotaria citrea, Accentor modularis,
and J/cterta virens, and how marvellously close is the similarity,
even to the most insignificant details (barring the one less facet
on either costal border, in the case of the second-named species) ;
and if guided alone by their form, how difficult it would be to
distinguish them without any other assistance! And yet, were
the sternum of Psaltriparus plumbeus brought up to the size of
the sternum in the Prothonotary Warbler, we would have no
difficulty in such a matter, notwithstanding the fact that the
general pattern in both is the same; and how extraordinary is
the gentle gradation in form between two such species, in this
part of their skeletons, with respect to species of intermediate
affinity !

On the Appendicular Skeleton: the Pectoral Limb. — As is
usually the case, the several bones of the limbs of these small
passerine birds offer us but a slender list of distinguishing char-
acters, in any way pointing to the affinities of the species com-
pared. In Chamea the bones of both extremities appear to be
completely non-pneumatic, whereas in such a Tit as the Parus
znornatus both the humerus and femur have air admitted to
their shafts; and I am not certain but that the long bones of
the antibrachium and leg are in the same case. Other Tits also
have the arm and thigh bones pneumatic. The Awmerus in our
subject is characterized by having a notably straight shaft, and
for its brevity, as compared with the size of its owner. Its head
and distal extremity, however, are in harmonious proportion with
its length ; while the small glenoid cavity of the shoulder girdle,
intended for its articulation, is re-inforced by a fair-sized os
humero scapulare, in which it agrees with other species and
genera before me.

_ Both bones of the antibrachium, the vadzus and ulna, are like-
wise very short and very straight. This may be best appreci-
ated by stating the fact that the radius in Psaltriparus plumbeus
comes within a hair’s breadth of being fully as long as that bone

494 SHOUFELDT. [Vot. III.

in the forearm of Chamea, yet see the difference in the size of
the skulls of these two birds in Figures 1 and 3. Another way
we have of contrasting such a matter is by the fact that the
tibio-tarsus in Chamea is very nearly three times the length of
its radius, and the tarso-metatarsus is nearly double its length.
Nothing specially noteworthy is met with in the skeleton of the
pinion in our subject. Measured from the head of the carpo-
metacarpus to tip of the most distal phalanx, this division of
the skeleton of the pectoral limb is nearly as long as the ulna.
The Bush-Tits have these parts quite in proportion with the size
of their bodies, but otherwise the form of the bones is pretty
much the same.

Parus inornatus (Lophophanes) presents some peculiarities in
the skeleton of its antibrachium and pinion, for the outer sur-
face of the proximal third of the shaft of the radius always
develops a scale-like projecting ledge. While the proximal] pha-
lanx of the index digit is flat and smooth upon its radial side,
it is deeply excavated for the entire length of its anconal aspect ;
and finally, the slender middle digit extends for an unusual dis-
tance below the main shaft of the carpo-metacarpus (or index
digit), allowing its rather large and single phalanx to descend to
a point considerably below the middle of the hinder margin of
the proximal phalangeal joint of the index finger, whereas, as
we know, in most birds it is stowed away in the recess at the
upper third of this joint. Chamea also reveals its parine affini-
ties in this particular, for the skeleton of its pinion is constituted
pretty much on the same plan.

Wrens have their arm-bones a good deal like we find them in
the Paring, but here a noticeable flattening of the radius always
seems to be present, and characterizing the proximal moiety of
the shaft of the bone.

Accentor modularis offers us nothing peculiar in its skeletal
wing structure worthy of especial note; it is formed upon a
strictly passerine type.

The Pelvic Limb. —So far as the characters of the bones of
this limb themselves are concerned, they present so few strong
differential ones to assist us in determining affinities that we
might with great propriety pass them by at this point, but still
a word in regard to other matters concerning them will not be
out of place. In Chamea all the long bones of the pelvic limb

No. 3.] POSITION OF CHAMA. 495

are conspicuous for their slenderness, and in the case of the
tibio-tarsus and tarso-metatarsus, for their unusual length; the
femur in this species is relatively very short, and is convexed
forwards near its middle. To show some of these discrepancies
in length we have but to present a few measurements : —

TABLE.

(Metric Measure.)

SPECIES. se NE oN Ar oa ite
Chamea fastiata......-. 3.1 cms. MOrems=) |) 3-3) cms. || 2-5 Cums.
Parus tnornatus griseus. . .| 31 * Er tess zo. Zin ts
Salpinctes obsoletus.....- Sites OF fs ai Bee no. “
Psaltriparus plumbeus... .| 18 * Relvest® Baty 5 5a ee

As in the vast majority of all true oscines, —indeed I cannot
recall an exception to the rule, — Chamea possesses a small pa-
tella at the front of its knee-joint embedded in the usual tendon.
With respect to the ¢7bzo-tarsus, its cnemial crest is seen to rise
well above the articular surface of the summit of the bone; and
both its pro- and ectocnemial processes are well-developed.
Distally the condyles are very prominent anteriorly, their outer
peripheries being nearly exactly alike in outline, and of a uni-
form shape.

The shaft of this bone is wonderfully straight and of nearly
the same calibre from one end to the other. Its associate in
the leg, the fibula, is of very diminutive proportions, freely
attached, and ossifies for only a short distance below its ridge for
articulation on the shaft of the tibio-tarsus. Zarso-metatarsus
also has a straight shaft, for the most part flattened in front
and rather sharpened behind. The hypotarsus is comparatively
prominent, and shows both grooves and canals perforated for the
passage of tendons. At its extremity, the mid-trochlea is seen
to be situated the lowest upon the shaft, and all three of these
projections are very much in the same plane, or the one, approx-
imately speaking, in which the anterior flat surface of the shaft
may be said to lie.

496 SHUFELDT. [Vou. III.

The “accessory metatarsal”’ is comparatively large as com-
pared with the associated parts and supports a strong basal
joint for the hallux digit. This is also the case in Salpinctes,
another species which spends much of its time on the ground.

The arrangement of the joints of the toes, 2, 3, 4, and 5, for
hallux to fourth toe respectively, is strictly passerine and -pre-
sents nothing worthy of especial remark.

Aside from what I have pointed out then in the last few para-
graphs touching upon the pelvic limb, the ornithotomist may be
well assured that no vantage is to be gained, so far as the eluci-
dation of affinities go, by entering upon a detailed comparison
of the several characteristics presented in these bones of the
supposed affines of Chamca, for such characters are not of a
nature of sufficient import to be brought into the discussion
with any telling results, and the attempt to utilize such other
insignificant differences as I have intentionally passed over,
would simply be a profitless task.

In passing, I would say here that I have carefully compared
in the present connection the skeleton in Lophophanes with a
skeleton of Pertsoreus c. capitalis, and find the latter to be
essentially a garruline bird in so far as its osteology goes, and
very easily distinguished from any Tit in our avifauna. It was
Coues who said of our Parzde that, “really they are hard to
distinguish, technically, from Jays; but all our Jays are much
over seven inches long.”! The resemblance, aside from the
question of size, and to a lesser extent, of color, in the case of
Perisoreus and Lophophanes, is brought to mind by the agreement
in the case of the corresponding morphological details exempli-
fied by the majority of the external characters. It is imme-
diately dispelled by a comparison of the skeleton in the two
genera in question ; though there may, however, be some remote
affinity here.

In that Chamea lays plain greenish blue eggs, of course means
something ; especially as all our Wrens and Tits, as a rule, lay
white eggs that are more or less spotted. Such a single charac-
ter, however, often persists in a species, being carried down
from the original ancestral stock, and to it no unjust weight
must be attached. Then, too, it must be remembered that
Chamea being related to the Wrens, and these latter surely

1 Key to North American Birds, 2d ed., p. 263.

SPECIES,

1. Chamea fasciata.

2. Psaltriparus plumbeus.

3. Campylorhynchus brunneicapillus.

GENERAL FORM OF THE
SKULL.

Brain-case ample for size of
bird; not ae vertically
compressed. Skull somewhat
acutely produced — SLORY
and superior mandible slightly
decurved,

Brain-case = ditto. Skull
less acutely produced ante-
riorly as compared with
Chamea ; superior mandible
only slightly decurved.

EXTERNAL NARIAL
APERTURE OF SKULL,

Each rathera large, lon-
gitudinally placed, sub-
elliptical opening.

ditto.

Brain-case less ample as
compared with Chamea ;
somewhat vertically com-
ressed. Skull proportionate-
ly very much more produced
anteriorly than in Chamea,
Superior mandible decurved,

ditto.

4. Auriparus flaviceps.

5. Catherpes m. conspersus.

6. Parus i. griseus (Lophophanes).

Brain-case ample for size of
bird: not vertically com-
pressed. Facial portion short
and acute, Superior mandi-
ble slightly decurved.

Brain-case ample, and
markedly compressed in ver-
tical direction. Skull much
produced anteriorly; superior
mandible slightly decurved.

Each subcircular in
outline. Very different
from Cham@a or the
Bush-Tits.

Each a long, narrow
subellipse in outline.

Brain-case rather large, and
semiglobular in form. Face
of skull short; superior osse-

ous mandible in no ways de-
curved,

. Troglodytes a. parkmanii.

_

8. Salpinctes obsoletus.

9. Aigithaliscus erythrocephalus,

Brain-case rather small
comparatively; slightly com-
pressed. Skull produced an-
genEEY Superior osseous
mandible decurved.

Each subcircular in
outline.

Each a large, longitudi-
nally placed, subelliptical
opening.

INTERORBITAL
SEPTUM.

Shows a large central
vacuity, and another
similar opening above.

VoMER.

Swelled anteriorly
where it is truncated
and mesially notched.

TABEE.

PALATINES.

Rounded postero-ex-
ternal angles; anterior
limbs very slender.

MAXILLO-PALA-
TINES. ©

Each mesial end rath-
er large, flat, thin, and
squarish. Not in’con-
tact with vomer,

ditto.

ditto.

ditto.

ditto.

With notably small
vacuities in it.

Much the same.

More uniform in cal-
ibre throughout. Onl
a shallow rounded note!
in front.

Postero-external an-
gles inclined to be more
squarish, otherwise dit-
to.

Somewhat produced
and pointed postero-
external angles. Ante-
rior limbs slender,

Vertically com-
pressed; enlarged ante-
riorly and unnotched.

Much as in the typi-
cal Wrens generally.

Narrow -leaf-shaped,
and so fornted in front.

As in Campylorhyn-
chus.

Appears to be doubly
notched in front, other-
wiseas in typical Wrens,

ditto.

ditto,

Brain-case fairly ample;
slightly compressed vertically;
moderately produced anterior-
Wi superior mandible slightly

lecurved,

Each rather large, sub-
elliptical.

ditto.

ditto.

Postero-external an-
gles produced as Jong,
sharp spines.

Postero-external an-
gles ot produced,
though angular. Ante-
rior limbs /ong and
slender,

Short: postero-ex-
ternal angles truncate.
Anterior limbs compar-
atively stouter.

As in Campylorhyn-
chus.

Quite similar; mesial
paddles comparatively
thicker.

Mesial ends narrow
and longitudinally pro-
duced, Quite different
from Chamea.

Much as in Chamea.

As in Campylorhyn-

chus.

MANDIBLE.

Moderate V in out-
line; rather feeble; a
fair-sized, elliptical ra-
mal vacuity. The base
slightly decurved.

ditto.

Acute V in outline;
rather strong, and de-
curved. Ramal vacui-
ty absent.

V-shaped ; subcircu-
lar ramal vacuity pres-
ent; angular processes
markedly produced be-
hind.

Acute V-formed; de-
curved; feeble, and ra-
mal vacuity exceeding-
ly minute.

SHOULDER-GIRDLE.

STERNUM.

PELVIs.

Coracoids long and
slender, shafts straight
and _ subcylindrical.
Scapula: curved out-
wards pestenony: Hy-
pocleidium of Ustarctita
small.

ditto.

Coracoid proportion-
ately very much short-
er, others nearly ditto
for the remaining bones
of the arch,

Coracoids not strictly
parine. Scapul rather
smartly bent at posteri-
or thirds ; hypocleidium
comparatively larger.

Bones all strikingly
slender; scapula short
and dent atends; hypo-
cleidium of furcula mi-
nute.

Two-notched; sub-
oblong in outline; shal-
low carina, lofty costal
processes; large bifur-
cated manubrium.

ditto; carina propor-
tionally somewhat deep-
er.

Proportionately more
oblong than in Cha-
mea ; otherwise ditto.

Tlia meet over sacral
crista; a double parial
row of pits down ven-
tral surface of sacrum.

Ilia very nearly meet
over sacral crista; oth-
erwise ditto.

ditto; sacral row of
pits nearly obsolete.

ditto to last, but its
keel — comparatively
much deeper than in
Chamea.

Square in outline;
carina shallow, and
withal the bone flatter
than in Chamea.

Mesial ends Jarge,
squarish, thin, and flat:
not touching vomer,

As in Campylorhyn-
chus.

Strong; a V in form;
large subelliptical ra-
mal vacuities,

Rather feeble; a V-
shaped one with asmal/
elliptical ramal vacuity.

ditto.

As in Chameaa,

Much as in Psaltr?-
parus.

As in Psaltrifarus.

ditto.

Each free mesial end
flat, thin, and squarish.

Ramal vacuity absent.

Short, slender cora-
coid; scapule narrow,
with ends curved out-

ward; _hypocleidium
rather large,
Like the typical

Wrens, and with the
hypocleidium of furcula
larger.

ditto.

Oblong; compara-
tively deep carina;
large, broad costal pro-
cesses.

Suboblong in out-
line; carina of moder-
ate depth. Processes
all well developed,

ditto.

Much as in the Bush-
Tits.

Resembles Psaltri-
parus plumbeus.

Quite as we find it in
the U.S. Bush-Tits.

Tlia well separated
from sacral crista. Pits
of sacrum beneath,
scarcely perceptible.

Tlia do not meet sa-
cral crista. Pits on
sacrum nearly obsolete.

Tlia rather widely sep-
arated from sacral cris-
ta; rows of sacral pits
distinct,

Tlia well separated
from sacral crista. Pits
beneath sacrum very
marked.

ditto.

Ilia meet the sacral
crista. The double row
of pits present.

REMARKS,

Has the habit of occasionally carrying tail
erect like a Wren (Gambel); ‘inhabits
“shrubby and weedy places, is restless and
active, expert in eluding observation, and
clamorous in resenting intrusion of its haunts,
with harsh, scolding notes” (Coues), Ex-
ternal characters are given in another Table
(antea).

Gregarious at certain seasons. Nearly all
Titmice have a scolding note wherewith they
greet intruders who chance near their nests,
or in many cases, even their haunts.

A large Wren, approaching Harforhyn-
chus in its structure.

A Tit, nearest related to Psaltriparus
among our United States Parrde, but with
mutch in its structure connecting it with the
genus Compsothlyprs among the Mniotilt:-
dz. Almost a form that stands between the
two families referred to.

A peculiar species of Wren, having a skel-
eton wherein the skull by its fatness at once
distinguishes it from other genera of Wrens
in our United States ayifauna.

Tits which are osteologically quite distinct
from any other genus of the Parrd@ of the
United States, and equally so from Chamea.

A typical troglodytine species.

Osteologically, this Wrenis nearer Cather-
fes in its affinity than it is Campylorhyn-
chus.

This little Titmouse from the N. W. Hima-
layas, osteologically comes near our genus
Psaltriparus, and in some particularss es-
pecially in the skull, nearer Chamea,

No. 3.] POSITION OF CHAMAZA. 499

being related to the Mimine, in that subfamily we find
such a form as Galeoscoptes carolinensis, which not only lays
greenish blue eggs, but also sometimes has the tarsal scutella
obsolete (it being generally so in Chamea). This and other
minor points present themselves which will keep the fact before
our minds that originally all these forms came from the same
stock, and in the divergence which has subsequently taken
place, in time, species have been created that are now remotely
affined, as are such forms as Galeoscoptes carolinensis and Cha-
mea fasciata. Still Darwin has shown how such characters as
I have mentioned above may be retained by the now more dis-
tantly related forms, and be transmitted by them.

So far then as the color of its eggs are concerned, it, as a char-
acter, points to the troglodytine affinity of Chamea, probably in
the way I have indicated, as birds directly related to the Wrens,
as we have just seen, lay greenish blue eggs, and we are thus
not compelled to pass beyond the limits of the family lines to ob-
tain a likely explanation of this fact. At the present time I do not
recall any typical parine form which lays an unspotted blue egg.

Recently I have had the opportunity of examining both
Campylorhynchus brunneicapillus and Auriparus flaviceps in the
flesh, several specimens of each. The former has all the char-
acters of a large Wren, more nearly related to the species
associated in the genus Harporhynchus than are any of our
smaller Wrens; while the latter, notwithstanding its peculiar
coloration, and some other non-strictly external parine charac-
ters, has a skeleton essentially very much like that part of the
anatomy in Psaltriparus and its allies.

Before recapitulating the skeletal characters for comparison,
of a number of the species we have been examining in the
present connection, I would again lay stress upon the fact that
in so far as its topographical anatomy and characters are con-
cerned, Chamea shows a far closer kinship with Psa/triparus
than it does with any of our typical North American Wrens.
In the matter of coloration simply, its predominating shades of
brown seem to point Wren-wards ; still we must remember here
that in the case of the inland form of Chamea (C. f. henshawt)
the prevailing tints of the plumage are of a grayish ash, which
Coues admits is “about the color of a Lophophanes.” 1} Already

1 Key, 2d ed., p. 262,

500 SHUFELDT. [Vot. III.

I have said, that when the species now grouped in the genus
Ciunicerthia come to be anatomically examined and carefully
compared, they may show quite as much of the Tit in their
organization as they do of the Wren. Indeed, they may stand
directly between these two groups of birds, and the new C7zzz2-
certhia described by Mr. Sharpe in the Catalogue of the British
Museum, may prove to have far more of the Wren in it than
has Cinnicerthia unibrunnea; or still more than C. wnzrufa.
Our hard and fast lines in systematic classification are a little
binding sometimes, and do not strictly define the delicate rela-
tionships existing among such forms as go to make up the class
Aves.

CONCLUSIONS.

It is only when one comes to investigate the morphology, in
its entirety, of the smaller passerine birds, that it can in any way
be appreciated how thickly the twigs stand upon that branch of
the genealogical avian tree. As they have forked and split up,
and been derived from each other, so have the bird forms which
now represent this branching growth, become distinct in their
thousand and one species, and in each we may look for inherited
characters that likely they assumed and appropriated from a
variety of ancestors at various stages of their derivation and off-
shooting. Thus it is that we may come across a species of bird
wherein the main trend of its morphology and organization is
indubitably stamped with all the characters of the stock-branch,
or that off-shoot where all those of its kind could be designated
as clearly differentiated Passeres for instance, and yet it will
show in different degrees tinctures in its make-up that have been
borrowed by its economy from the earlier branchings that pre-
ceded it.

We may have a passerine bird presented to us, to offer an
hypothetical case, which, to all intents and purposes, is in its
entirety a representative of the great group which we have
defined by that name. It may be the most fixed species of its
genus, and yet when we come to study its structure in ad// its
details, how puzzlingly do the anatomical evidences of its affinity
crop up. So dilute may have some of the blood of remotely
affined tribes run into itself that it lies quite beyond the power

No. 3.] ' POSITION OF CHAMEA. soI

of man to detect them, much less accurately state from whence
they were derived. Then again, other characters present them-
selves which almost stand boldly out in their significance, and
point but in one direction to the kindred stock responsible for
them. Who is the one among us who can truly tell just exactly
how much of S¢eatornts is Owl, or how much typical picine
stock there is in Yusr? And such problems are even still
harder to solve where the affines are thickly clustered, and such
are the difficulties we meet with when one attempts to unravel
the ancestry of such a species as Chamea fasciata.

Apart from its larger size, there is no question, after we have
stripped specimens of all our United States Wrens and Titmice
of their feathers, but that the general form of a Chamea is more
like a Bush-Tit (Psaltriparus) than it is like any of the rest of
them, and this resemblance is real. Not to pass beyond the
avifauna of this country then, we have shown in the text how
this resemblance is again supported by the anatomy of the “soft
parts,’— greater preponderance of characters of these birds
being found in Chamea over its troglydytine ones. Coming to
the skeleton, a part of the organization from which we have the
right to draw upon for our conclusions, it being one of the most
reliable systems, and one which long retains the indices of a
vertebrate’s affinities, we see, at least, something to assist us in
pronouncing upon the kinship of Chamea.

Surely no one could be made to believe that Chama@a bears
any close osteological resemblance to such a form as Catherpes
m. conspersus. The short-faced, semi-rotund skull of the former,
with its maxillo-palatines having their free mesial ends large,
thin, flat, and sguarish; with its palatines having rounded pos-
terior-external angles, and with a differently formed vomer and
mandible ; — certainly all this is quite at variance with the long-
faced, strikingly flattened skull of the latter, with its maxillo-
palatines having their free mesial ends zarrow, thin, and
posteriorly produced; with its palatines having their postero-
external angles produced and angular; and finally, with the
differences in the vomer and mandible spoken of in the text of
this monograph. These cranial differences, as we now know,
are also supported by others in the trunk skeleton in the two
species in question. Withdrawing, then, such a formas Catherpes
m. conspersus, we find it followed by its evident allies in our

502 SHOUFELDT. VoErcrir,

fauna, the representatives of the genera Troglodytes, Salpinctes,
Campylorhynchus, and others, although many of these show,
perhaps, a somewhat closer affinity with Cham@a than does
Catherpes, but behind that fact it still remains clear that they are
all WRENS in every sense of the word. Campylorhynchus, which
by some has been supposed to be nearer Chamea, has a typical
Wren’s skull, and one reminding us not very much of the Wren-
Tit.

One of the best cranial characters distinguishing these birds
is to be found in the form assumed by the free mesial extremi-
ties of the maxillo-palatines ; these differences I have already
clearly defined above, and they are constant ; and furthermore,
these parts are alike in Chamea and Psaltriparus, and differ
from all the Wrens. The sternum offers us hardly a distinguish-
ing character, but it would seem that the fact whether or no the
ilia meet the sacral crista mesially should have its weight, and
here Campylorhynchus is the only Wren that agrees with Chamea
in that particular, whereas the Bush-Tits practically add this
feature to the other list of characters that force us to believe
them to be more nearly related to Chamea than any other species
of bird at present known to our avifauna.

As I have already stated, judging from topographical anatom-
ical characters alone, I am strongly inclined to think that
Chamea fasciata may be related to the Cinnicerthia unirufa, of
Colombia, but I am also convinced that that latter species is
not a whit nearer in its affinity to such a Wren as is Catherpfes
m. conspersus, than is Chamea.

Whether Ctunicerthia has any parine affinity, and just how
much, is a question, I believe, that still remains for the mor-
phologist to decide.

ERRATA AND ADDENDA

TO

VoLuME III., Part 2.

Page 142, line 21 from top; for ‘‘ digits,” read phalanges.
«« 178, ‘** 7 from bottom; for ‘‘ chance,” read change.
** 182, ‘* 19 from top; for ‘‘ commences,” read commenced.
‘* 203, ‘* 14 from top; insert after ‘‘ water,” the words, and air.
Ti 2o5 ys Sts dor + these,” read. their.
‘¢ 208, ‘* 10 from top; after ‘‘ placed,” add the words, over or.
«© 208, ‘* 15 from top; for ‘‘ invertebrates,” read vertebrates.
“© 215, ‘* 2 from top; for ‘‘ metapophysis.” read metapophyses.
ks orn7. << 15 from top.; for ** cause,” read use.
<* 240, ‘* 14 from top; for ‘“‘ away,” read way.
** 248, ‘* at bottom of page; insert, after Gaudry.
‘** 261, last line of explanation of Fig. 83; for ‘‘ external,” read interme-
diate.
** 266, last line of explanation of Fig. 87; for “tympania,” read tympanic.
‘* 268, first line of explanation of Fig. 90; for ‘‘ (a),” read (¢).
‘* 273, line 7; before ‘‘ assertion,” insert the word naked.
“277, ** 13 from top; for ‘‘ transverse,” read longitudinal.

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