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ends of the otic capsules and fusing in the broadly ex-
panded ethmoid phite. In the median line the ethmoid
plate is continued forward into the nasal septum. At
the sides of the posterior end of the septum the ethmoid
plate is perforated by the olfactory foramina {ol). A
triangular lamina cribrosa (I) projects outward, down-
ward and forward from each antero-lateral margin of the
ethmoid plate. This and the septum with the connecting
rods compose the nasal capsules.

From the ventro-lateral margin of the lamina cribrosa
(Fig. 21) a slender cartilage projects horizontally inward
to beneath the inner border of the lamina where it splits
into two cylindrical rods, a dorsal and a ventral. The
dorsal rod {d) extends forward inward and upward to the
antero-dorsal point of the septum, while the ventral rod
(vjp) curves sharply inward, touches the ventral margin
of the septum and then, slightly expanding in width, ter-
minates in a process projecting freely forward. A small
foramen for the orbito-nasalis, seen only when the skull is
viewed from below (oji), passes beneath the posterior end
of the lamina-cribrosa just outside the anterior end of the



112 BULLETIN OF THE ESSEX INSTITUTE.

trabecula. The short so-called ' palatine cartilage ' is,
as has been shown by Gaupp, the homologue of the ant-
orbital process of the Urodela.

The quadrate is situated much nearer the posterior end
of the skull than that of the Urodela described. It lies
about under the middle of the lateral wall of the otic cap-
sule, to which it is connected by means of a dorsal otic
and a ventral palato-basal process. There is no stapedial
process connecting the quadrate directly with the stapes,
but, as was mentioned above, the stapes is connected with
the tympanic annulus which is earlier derived from the
quadrate. A slender palato-pterygoid process {ppt)
projects forward from the body of the quadrate and fuses
with the lateral margin of the lamina cribrosa. The rela-
tively posterior position of the quadrate adds proportion-
ately to the length of Meckel's cartilage.

Anura and Urodela contrasted.

From a general view of the chondrocrania of these two
groups it is seen that, on the whole, in the Anura the width
is greater in proportion to its length than in the Urodela.
But since there are many very short and broad skulls
among the Urodela this distinction is of little value. The
closure of the cranial cavity is more complete in the An-
ura, especially in the ventral region whore the basicranial
fontanelle, as shown by Gaupp ('93), becomes greatly re-
duced. Here, too, instead of ending freely, the pterygoid
process of the quadrate is attached anteriorly to the eth-
moid plate. In these two last mentioned points the Anura
show more resemblance to the Selachians than do the
Urodela.

We may here insert a few words in regard to the ho-
mologies and terminology of the cartilages which have



THE CHONDROCRANIUM IN THE ICHTHTOPSIDA. 113

been variously called the ' antorbital process ' and the
'palatine cartilage.' Gaiipp ('91) maintained the homol-
ogy of the ' antorbital ' of the Urodela with the palatine
of the Anura. Speaking of this cartilage in Amphiuma,
Kingsley ('92) said, "the lower process may retain the
name, antorbital, usually applied to it, for Amphiuma
presents no evidence that it is the palatine cartilage as
Gaupp interprets it." In his final paper on the chondro-
cranium of Rana, Gaupp ('93) repeats his former position
and, stating that he uses the two terms interchangeably,
comments upon the above quotation as follows : " Kings-
ley scheint unter 'Palatine Cartilage ' hier etwas Besond-
eres zu verstehen ; was das ist, kann ich aus seinen
Angaben nicht ersehen."

There seems to be no doubt as to the correctness of the
homology of the cartilages as pointed out by Gaupp. The
question here, however, is one of terminology and it is
not to be settled by the fact that certain authors have
called this cartilage the palatine, but upon the broader
grounds of comparative anatomy, and here the question
of priority must also be taken into account. The term
palatine bone in some of its various modifications was first
applied to a bone occurring in the palatal region of the
Mammalia, and, in transferring the name to other classes of
vertebrates, it is obligatory that it should be given only
to those structures which are homologous with the palatine
of mammals. That the palatine bone of the Amphibia is
homologous with the palatine bone in the mammals I do
not deny, but I maintain that this cartilaginous process is
in no Avay a palatine process but that rather its relations
are with the nasal capsule, and for the following reasons :

In the mammals the palatine bone is regularly enum-
erated among the membrane bones (Minot '92, inter alia)
and, so far as I am aware, it has no connection with any

ESSEX IN8T. BULLETIN, VOL. XXVIII 8



114 BULLETIN OF THE ESSEX INSTITUTE.

cartilage. To attempt to homologize a membrane bone
with a cartilage is a difficult task. If, however, it be
maintained that we have here a case of substitution such
as exists in the roofing bones (parietals, frontals, etc.) of
the cranium, in which the cartilaginous roof of the brain
cavity becomes replaced by the immigration ot dermal
bones, Ichthyophis throws considerable light upon the
question. In this form the palatine bone (part of the
maxillopalatine process of the Sarasins), which is distinct
in early stages, arises, not in connection with the cartilag-
inous process in question, but with the nodule of carti-
lage shown in Figs. 22, 23, and 24, j9c. In Ichthyophis
not only is this true cartilaginous ' palatine ' present but the
antorbital process occurs as well.

If we adopt the usually accepted homologies (which,
however, are not beyond question) the palatine of tbe
higher vertebrates is to be sought in the anterior portion
of the upper jaw of the Elasmobranchs, which is accord-
ingly called the palato-pterygo-quadrate or some similar
terra, implying homologies with the palatine of higher
forms. In these very Elasmobranchs, however, the exact
homologue of this antorbital process exists, in no way
connected with the upper jaw but rather as forming a part
of the nasal capsule.

The transformation during metamorphosis from a con-
dition in which the jaw of a small suctorial mouth articu-
lates with the anterior end of the pterygoid cartilage to
one in which it reaches back to the body of the quadrate
beneath the middle of the otic capsule is one of the most
striking characteristics of the Anuran chondrocranium.
Another of its distinctive features is found in the auditory
apparatus. While in the Urodela the fenestra ovalis may
be occupied by a cartilaginous stapes which may or may
not be connected with the quadrate by a stapedial process,



THE CHONDROCRANIUM IN THE ICHTHYOPSIDA. 115

in the Anura we find a much more complicated condition.
The fenestra ovalis passes through important changes of
form and the stapes comes into connection with a tym-
panic annulus. But if the tympanic annulus was "orig-
inally a postero-superior leaf cut off from the mandibular
suspensorium," as stated by Parker and Bettany ('77),
the fundamental similarity of the conditions in the two
groups is apparent. In connection with this point Gaupp
says, "Der vom Quadratum losgeloste knorpelige Annulus
tympanicus scheint eine dem Anuren allein zukommende
Bildung zu sein." Here, as with the Urodela, the nasal
capsule offers little that is of classificatory value.

The chief" points of difference between the chondrocra-
nium in the two groups may be tabulated as follows :

Urodela. Anura.

1. Both broad and narrow types. 1. Generally, if notalways, broad.

2. Pterygoid free in front (ex- 2. Pterygoid attached to ethmoid

cept in Ranodon). plate.

3. Basi- and supra-cranial fonta- 3. Basi- and supra-cranial fonta-

nelles large. nelles smaller.

4. No metamorphosis. 4. Very striking metamorphosis.

6. Auditory apparatus compara- 5. Auditory apparatus, including
tively simple. the tympanic annulus, com-

plex.

ICHTHYOPHIS GLUTIN08US.

First stage. — (Figs. 22 and 23). — The specimen from
which the model for this stage was made was a young
embryo still spirally coiled within its membranes. While
in some places, more particularly toward the anterior end
of the head, the tissue modelled is not true cartilage, the
differentiation of all the parts is sufficient to cause little
difficulty in distinguishing them.



116 BULLETIN OF THE ESSEX INSTITUTE.

The notochord occupies its usual position at the poste-
rior end of the cranium ; but, as it passes forward, it bends
downward so that its anterior end lies considerably be-
low the general level of the cranial floor. The para-
chordals are represented only by a narrow band of cartilage
connecting the posterior ends of the otic capsules. In
the median line the notochord is embedded in this band.
At its lateral margin the parachordal band fuses with the
occipital process behind and with the otic capsule in front.
The dorsal end of the occipital process is fused with the
otic capsule. Between these three cartilages is the jugu-
lar foramen {j) .

The otic capsules are longer, narrower and deeper than
those of Ambly stoma, and, as is usual in the younger
stages, they are comparatively widely separated. In the
median wall of each capsule are two foramina, a larger
anterior and a smaller posterior foramen. The ventro-
lateral wall of the capsule is largely taken up by the fen-
estra ovalis along the dorsal part of which lies the stapes.
The stapes is continued forward into a process which
reaches the posterior surface of the quadrate. This pro-
cess may retain the name ' stapedial process,' although in
this case it is continuous with the stapes rather than with
the quadrate. The stapes is perforated in a dorso-ventral
direction for the arteria perforans stapedia (Fig. 23, as).

Three processes arise from the anterior end of the otic
capsule. Two of these, which I shall call the dorsal {dr)
and ventral {vr) trabecular rods, extend forward in the
usual positions of the dorsal and ventral margins of the
trabecula. The third, and relatively much shorter process
is attached posteriorly to the otic capsule just below the
end of the dorsal trabecular rod. Curving downward and
forward it fuses with the ventral trabecular rod. In the
posterior end of the ventral trabecular rod there is a small



THE CHONDROCRANIUM IN THE ICHTHTOP8IDA. 117

foramen traversed by a nerve (apparently the palatine).
This foramen does not appear in the later stages modelled
but I am unable to give the details of the disappearance.

After passing forward separately to the orbital region,
the dorsal and ventral trabecular rods of each side are
connected by two narrow bands of cartilage, a post-
orbital {pob) and a pre-orbital {prb) between which the
elongated optic foramen {of) is enclosed. Beginning in
the region of the post-orbital band the dorsal and ventral
trabecular rods of each side, which have thus far been
approximately parallel, diverge in a horizontal direction.
The dorsal rod curves first outward and then inward,
giving off ventrally a plate-like lamina cribrosa near its
anterior end. The two ventral rods bend inward to the
median line where they unite to form a small ethmoid
plate. Just behind their point of fusion each ventral rod
gives off a ventro-lateral process which underlies the
posterior end of the olfactory vesicle. From the anterior
margin of the pre-orbital band of cartilage an antorbital
process (Fig. 23, anj)) extends outward and forward to-
wards the ventral portion of the lamina cribrosa.

The quadrate is composed of a l)ody, and ascending and
pterygoid processes. The ])ouy is small and stands out
from the side of the ventral trabecular rod below the an-
terior end of the ear capsule, with which it is not directly
connected. The ascending process passes upward and
forward and unites with the dorsal trabecular rod a little
in front of the ear capsule. The pterygoid process {pt)
is composed of two parts, a short proximal portion which
projects forward from the body, and an isolated portion
which later becomes the distal end of the process. This
method of development of the pterygoid is the same as that
mentioned by Gaupp ('91) for Siredon. A short dis-



118 BULLETIN or THE ESSEX INSTITUTE.

tance in front of the distal portion of the pterygoid is
another isolated rod of cartilage which runs in a direction
diagonal to tbat of tiie pterygoid process. This is the
palatine cartilage (pc).

Meckel's cartilage articulates with the ventral surface
of the body of the quadrate. Anteriorly the cartilages of
the two sides are still separated. They project backward
behind the point of articulation with the quadrate nearly
as far as the posterior end of the stapes (a).

Second stage. — (Figs. 24-26). — The parachordals
and occipital processes are in the same condition as before,
there being no trace of the formation of a synotic tectum.
The notochord has entirely disappeared from the head
region. The median wall of the otic capsule is more com-
plete than it was in the first stage (Fig. 25). What was
then the large anterior foramen is now divided into a
dorsal foramen for the endolymphatic duct (ef) and a
large ventral foramen for the auditory and facial nerves.
The floor of the capsule is now composed of a median and
a more lateral rod between which a fontanelle is enclosed.
The stapes and fenestra ovalis are in the same condition
as in the preceding stage.

The rod described in the first stage as connecting the
anterior end of the otic capsule with the ventral trabecular
rod now has a nearly vertical direction, the ventral end
being relatively more posterior in position than before.
As far forward as the orbital region there are no other
noteworthy changes. In the nasal region, howevei', im-
portant changes have occurred. Instead of the trans-
versely expanded nasal region of the earlier stage, we now
find the anterior ends of the dorsal trabecular rods folded
inward toward the nasal septum and forming a roof over
the sides of the olfactory organs. By this movement the



THE CHONDROCKANIUM IN THE ICHTHY0P8IDA. 119

lamina cribrosa is brought into its usual position. Its
distal end is fused with that of the antorbital process thus
enclosing the orbito-nasal foramen (Figs. 24 and 26, ofi).

The ethmoid plate is larger in both directions than in
the first stage, and in the median line upon its anterior
half arises the nasal septum (ns) . In front, upon the sides
of the base of the septum, the ethmoid plate terminates in
short free processes. The nasal septum is divided anteriorly
into three parts, a short median process which projects
freely forward, and two lateral bands which curve forward
and outward. At its most anterior point each of these
bands divides into a dorsal and a ventral process. These
extend backvvard along the lateral surface of the olfactory
organ and fuse with the outer end of the cartilage men-
tioned in the first stage as arising from near the anterior
end of the ventral trabecular rod. Where these three
processes meet a plate of cartilage is formed which lies
below the lamina cribrosa and is connected with it l)y a
short narrow band. No tectal cartilage is formed in the
chondrocranium of Ichthyophis.

As a result of ossification the ascending process of the
quadrate has lost its cartilaginous connection with the dor-
sal trabecular rod (Fig. 24), and the parts of the ptery-
goid process are now united into one continuous rod.
The body of the quadrate remains essentially unchanged,
it having neither otic nor palato-basal process. The two
cartilages of Meckel are now confluent in front, and the
palatine cartilage still remains isolated from the rest of
the chondrocranium. It appears that the ancestors of the
Batrachia had a palato-pterygo-quadrate cartilage similar
to that found in sharks. Of these cartilages the Urodeles
as a rule retain only the pterygoid and quadrate portions.
The Cfecilians have these two parts and an isolated pala-
tine portion, while in the Anura all three parts are united



120 BULLETIN OF THE ESSEX INSTITUTE.

in one rod which is joined in front to the antorbital
process.

The C^cilian Chondrocranium.

There are two views according to which the Ceecilians
are related to Amphiuma. According to one — the theory
of Cope ('89*) — the Caeciliaus are the extreme of a line
of degeneration from the typical Urodele stock and Am-
phiuma is one of the intermediates of the series nearest to
the Gymnophiona. Indeed, Cope goes so far as to make
the Csecilians merely a family of the Urodeles. The other
view is that of the cousins Sarasin who hold that Am-
phiuma is a neotenic Caicilian, a larval Csecilian become
sexually mature while retaining their branchial respiration.

According to the first view Amphiuma, and to a less
extent the rest of the Urodeles, must be <ilosely similar in
cranial as well as other structures to the young Csecilian.
Farther, if we find that Amphiuma and the Urodeles
have lost certain features which belonged to the ancestral
Craniota, the retention of these characters by the Csecil-
ians would be an aro-ument a2:ainst the line of descent
advocated. The view of the Sarasins presents even more
difficulties for we have both horns of the dilemma. If
Amphiuma be merely a Csecilian arrested in a larval con-
dition, then we have to say either that Amphiuma is not
related to the remaining Urodeles or that they have all
sprung from a Csecilian ancestry. The objections to the
second view are so many and so weighty that we think no
one would care to defend it. The limbs alone are enough
to set it aside. As to the other horn, it would seem that
all the evidence we have regarding adult structure and
development as well goes to show that Amphiuma is far
more closely allied to the other Urodeles than it is to the
Csecilians, while the same matter of limbs, weak though



THE CHONDROCRANIUM IN THE ICHTHYOPSIDA. 121

they be in Amphiuma, throws the whole view out of
court.

There remains then but the view of Cope, and this is
to be tested by seeing if there be features in the Csecil-
ians which must have been inherited and which could not
have been inherited from an Urodele ancestor.

The parachordals of Ichthyophis are smaller than those
of any other form studied. The nearest approach to
them is found in Desmognathus where there are bands,
not present in Ichthyophis, connecting the anterior end
of the notochord with the otic capsules. No synotic tec-
tum is formed in Ichthyophis, though at one period in the
development of the skull small crests on the dorso-median
walls of the otic capsules represent the first steps in the
formation of a tectum. This appearance, however, is
slight and but transitory.

There is a difference between the manner of develop-
ment of the trabeculae of Ichthyophis and those of the
other Batrachia described. Instead of being developed
by the successive formations of a ventral rod, a trabecu-
lar crest and a connective rod uniting the crest to the otic
capsule, we have the dorsal rod developing simultaneously
with the ventral rod and equally well chondrified. The
dorsal rod, separated as it is from the ventral rod and at-
tached to the anterior point of the otic capsule, somewhat
resembles the supraorbital band of fishes. But the fusion
of the ascending process of the quadrate with the dorsal
rod and the relations of the two trabecular rods anteriorly
are clearly Urodelan characters. The quadrate is pecu-
liar, however, in having no otic or palato-basal processes.
Aside from the ascending process and stapes it is entirely
separated from the rest of the skull. Its position is the
same as that of the Urodeles. The stapes is perforated
for the stapedial artery.

ESSEX INST. BULLETIN, VOL. XXVIII 8*



122 BULLETIN OF THE ESSEX INSTITUTE.

But more important than any of the features mentioned
above is the existence of an isolated palatine cartilage.
This is especially noteworthy since it seems to furnish
strong evidence in opposition to the theory of the Uro-
delan ancestry of the Csecilians. Ranodon is the only
Urodele which possesses that portion of the palato-ptery-
goid arch which may be considered to correspond to the
palatine cartilage of Ichthyophis, while in Amphiuma
there is not the slightest trace of it. We may therefore
conclude that the condition found in Ichthyophis was not
derived from an Urodelan ancestor but from some more
primitive form.

The articular process of Meckel's cartilage is unusually
long in Ichthyophis. The nasal capsules, while differing
from all the others described, have no features of sufficient
importance to be of any especial classificatory value.

The evidence which I have found, chiefly from a study
of the chondrocranium, appears to me to be against asso-
ciating the Caecilians with any of the Urodeles and in favor
of keeping them in a distinct group coordinate with the
Urodela and Anura.

POLYPTERUS BICHIR (Fig. 27).

In 1892 the late H. B. Pollard kindly allowed Dr.
Kingsley to trace the outlines of the cartilages in the
sections of the head of his youngest Polypterus. From
these drawings I have made the chondrocranium in wax.
Since the skull of this same specimen has already been
described and figured by Pollard ('91) I shall deal
chiefly with points of value from a comparative stand-
point. For further details in regard to the relations of
the chondrocranium to the rest of the head, reference
should be made to Pollard's paper Avhich contains a



THE CHONDKOCRANIUM IN THE ICHTHYOPSIDA. 123

dorsal view of the skull and drawings of sections through
various parts of the head.

No cartilaginous occipital arch is present, owing, ap-
parently, to ossification. The otic capsule is large and
selachian-like in form. In its postero-lateral wall there
is a large aperture exposing portions of the posterior and
horizontal canals. This also is prol)ably due to ossifica-
tion. A small remnant of the hyomandibular cartilage (h)
lies in a groove in the dorso-lateral surface of the capsule.
That it formerly reached down as far as the posterior end
of the pterygo-quadrate cartilage is shown by the figures
of Pollard and others.

A thick synotic tectum covers the brain cavity in the
posterior two-thirds of the otic region. There are indica-
tions of a medial capsular wall separating the brain cavity
from the cavity of the capsule at its posterior and anterior
ends, but the gieater part of the space is entirely open.
The floors of the capsules are continuous with the basilar
plate which slightly exceeds the synotic tectum in extent.
A peculiar rod of cartilage (bo) projects a short distance
backward from beneath the middle of the basilar plate.
At the anterior end of the capsules there are upon each
side two foramina and a deep groove which is now open
in front and apparently represents another foramen the
anterior wall of which is ossified. A short bar of cartilage
passes across the external opening of the posterior of the
two foramina, dividing it here into two. The unossified
posterior end of the supraorbital band remains as a solid
lateral projection upon the anterior end of the otic cap-
sule.

There is a complete separation of the chondrocranial ele-
ments of the otic region from those of the orl)ital and
nasal regions. The supraorbital band (sb) passes an-
teriorly into a broad tegmen cranii (fc) which covers over



124 BULLETIN OF THE ESSEX INSTITUTE.

the anterior end of the cranial cavity and continues for-
ward into the roof of the nasal capsules. Ventrally a solid
plate of cartilage (<), the trabecular plate, forms a con-
tinuous floor beneath the anterior end of the cranial cavity
and the nasal capsules, and projects forwards as a short
and rather blunt rostrum (>). A small isolated plate
of cartilage (tc) occupies the middle of the supracranial
fontanelle, a remnant, as Pollard suggests, of a primitively
complete tegmen cranii.

The nasal capsule consists of a large cavity enclosed by
simple, broad plates of cartilage. Its floor and roof are con-
nected by a tall septum medially and two bands laterally.
The posterior of these two bands marks the boundary be-
tween nasal capsule and cranial cavity. There are three
large apertures in the capsule walls : behind, the olfactory
foramen ; in front, the foramen for the nasal duct (nl) ;
and between them a third in the lateral wall. Besides these
there are two small foramina in the border of the nasal


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