MONMOUTHSHIRE
1882,
under
the
title
of
almost entirely re-written,
editions of
allowing me
abridge
others,
besides
that the
in
an
easily
the
index.
W.
N.
PARKER.
Univbrsity
College,
Cardiff,
August,
1907.
344
LIVER
346
PANCREAS
 
ments of
It
must,
however,
be
borne
in
—but that
them,
two
characters,
while
external
conditions,
in
general
may
speak
of
the
the
A
thus
com-
pleted
four parts ;
is spoken
morula
blastula
(Fig.
3).
The
(Fig.
5).
The
brain. In an
as
well
as
to
the
and endoderm
of
Vertebrate
Embryo.
A^
aorte
now
will
form
the
notochord
somites
shown
become
constricted
off
in
the
one
Vertebrates
respiration as
Amniota
period.
Towards
the
close
of
this
period
the
allantois
gradually
undergoes
more
or
less
complete
reduction.
more
or
less
complete
reduction.
In
the
higher
amnion
to
extend
longitudinally
to
extend
longitudinally
through
the
body,
and
between
the
developed
not
out of the
tissue,
and
encloses
the
organs
sometimes
in
one
only.
bodies
consisting
epiderm
when
they
contents have
immediately
before
meta-
morphosis,
numerous
nothing
to
do
with
Amphibian
at
the
junction
of
and in function.
at
metamorphosis.
The
cornification
;
base
of
the
feathers
{arredores
plumarura).
are
independent
development
of
the
feather
and
against
the
cold,
and
further
each barb,
so as
to have
relations to
the latter
manus and of
the body
feather-tracts (pterylce)
scale-
like
Secondarily
they
appeared
are
not,
the
hair
is
seen
hair-cone,
which
stage
in
which
the
may be
most
They
are
large
are
present
on
the
tori
OF
yield the
which it wanders from the derm, which may also contain
pigment.
nearly
the
skin,
in
those
marsupial
pouch
{h.m.)
Potentially,
but as a
sink
pockets,
which
together
constitute
a pouch, and
degrees
of
perfection
in
a
number
of
the
Eutheria
elevated into
many
other
embryo, at a
be
indication of normal
in those
the
milk is produced
sheep have also
Elasmobranchs
is
the
primary
cause
of
plate, gradually
the
complications arise. To
cartilaginous
of the
Scales.
{e.g.
Plectognathi,
Lopho-
branchii,
form
a
strong
their situation
in
the
two
due
to
convergence.
Amphibians.
—Recent
Amphibians
armour
these,
specially
strong
dermal
correspond
cosaurus.
Reptiles.
—The
dermal
skeleton
by ossification
as
they
as a
adult an unpaired plate of varied form. It is wanting
in
Chamseleo,
to an
occur
between
these
this
exoskeleton
has
: more probably
consequence of its development
present
as
such.
ways.
It
may
which-
skeleton may
be of
membrane
which
covers
disappear in the course
the
meshwork
the
Notochordal
Sheaths
and
B.
notochordal cells
is
derived
paired
C.
D.
{A—D represent the caudal region,)
E.—
A
later
(?ic) has become
arch
of the vertebral
(e.g. Bony
without
tissue,
the
notochord
in
the
various
Vertebrate
groups
and
persist
of the
whereas in the
trunk,
gut, with
which it
Cyclostomes,
these
their
structure
is
more
complicated
in
elements,
which
Jim:
Fig.
38.
Portion
; A
and
C,
two
rib
somewhat
similar
is
be
seen
that
correspond
basidorsals
and
interdorsals.
less densely
notochord becomes
constricted by
in
the
anterior
convex
tail is
number
Eel, however, possesses more
thoraco-lumhar,
Vertebrates.
On
account
of
the
absence
of
The bony centra
enclose it.
: in the interior
of Urodeles
D, ScUamandriivob
transverse process
anterior
another from vertebra to vertebra,
and
one
column
is
rendered
of
the
higher
Vertebrates,
as
is
the part
becomes
The number
existing representative,
recognis-
able
As a rule
case
certain
Reptiles
process,
posterior
portion
the
vertebrae
usually
fuse
together
pygostyle,
which
supports
the
in
up
of
from
axis
; well-developed
articular
other
hand,
the
cervical
vertebrae
may
another
As in
primary
sacral
vertebrae,
but
;
intermiLSCular
larva of
52)
bony
bar,
arising
from
the
centrum,
and
bifurcated
to the
primary rib-rudiment,
the
rib-
bearing
never
and are
to the
tail, where
to
or
less
extent.
segmented
from
the
number
of
the
ribs
Crocodiles
bifurcated,
in
correspondence
with
gradually shifted, so that
and
ribs
end
freely
in
(p.
62),
vestiges
a
as
(Fig.
55).
It
must have
existing
Urodeles
(cf
p.
67).
the
ventral
portion
but
as
consisting
of
the
55,
B,
c).
the
two
and by the dorso-ventral
The latter occurs
relatively
in Triton
{Hemidactylus
verrucosus).
From
concerned
in
the
formation
of
the
sternum
of
(stcrnehw)
or
ensiform
process.
wherever
a
larger
surface
for
the
origin
in
the
Craniata
has
the
skull
the
base
of
the
skull,
skeletogenous
basis
as,
vertebral
axis.
More-
over,
the
cranial
considered as a
For
that as
 
of the
seemed
means clear
quite
conceivable
development, become situated
with
the
cranium,
and
thus
configuration
them later.
a solid
Above.
X
Fr.
Ziegler
Ascending
process^
various
the
nasal
sacs.
Anteriorly,
the
even
to
the
dorsal
for
example.
But
the
higher
the
systematic
position
as nine) in
in
some
mandihdar (Fig.
connecting the arch of either side and embedded in the
tongue
(cntoglossal
or
glossohyal).
homology
described as
nasal,
supraethmoid
of
Teleostei,
prefrontal
Mammalia
Amphibians
is
ossifications
arise the
sphenotic, and
the prootic. The
but unites
with a
fact
can
be
recognised.
in
the
various
groups,
and
to
give
here
the
merest
sketch
special
peculiarities
(Fig.
64),
are really
The
slightly
to the
behind
the
skull
( palceo-
cranium
be recognised.
be
described
as
hyostylic,
to
the
suspensorium.
In
Notidanus,
both
mandibular
bular, and leads into the
pharynx
probably represent
teeth have
smaller
in
the
Holocephali
it is always
as
65).
Externally
oral
cavity.
The
median
(Amia)
or
laginous byoid rays. A
derived from that
piscine
phylum.
a?:d
Orbital
and is con-
nected with the
skull-base anteriorly. In
a quadrate.
as
in
region
supraethmoid
and
lateral
the mouth, and
the bones in relation
bars. These
;
p.
82.)
ventral
parts
of
the
opercular
fold
or
bones.
The
chondrocranium
anterior
to
this
point.
of
the
chondrocranium,
on
the
;
angular and a
mode
of
life.
ing
a
compressed in
by a mem-
branchs
case
the
number
of
branchial
arches
are
nostril is bounded by
is
a
prefrontal,
and
medially
to
the oral
than
a
lower
zygomatic
plate,
and
AF)
;
to the
mandibular arch
or
74,
a),
sling-like
a much
they
{e.g.
Branchiosaurus)
Fr. Ziegler.)
apparatus, as
well as
especially
in
the
primitive
Hatteria
and
hand,
numerous
points
the two
embryonic
: it
may
be
represented
by
most
Reptiles
Prefrontals
and
be
a
postorbital
posteriorly
to
the
prefrontal
vomer,
in
most
of the
as well
more
cases
a
considerably : it consists
formed
by
processes
with the quadrate
by the quadrato-
and
paraquadrate, w^hile
absent
A
; viz., a
may
be
convenient
to
enumerate
them
palatine,
in
many
compara-
tively
late.
In
consequence
to
the
skull
by
means
of
the
Pttdc
Fig.
81.
Skull
of
( squamosal ); supra.
united
by
ligament.
The
most
cases
movably
articulated
frontals may
also become
the
to
the
In
the
orbito-temporal
regiou
there
is
hardly
any
cartilage,
even
here
can be recognised even
of
but
is
compara-
tively
little
There
is
a
large
parasphenoidal
rostrum
are
united,
and
doubtless
correlated
wdth
con-
in a
very w4de
articulates posteriorly wath
in
orbit
{e.g.
wall
of
the
of the anterior boundary of the
orbit
replaced
functionally
by
horny
larynx
of a
pair of
small hyoid
 
in
Length.
The cranial
formerly
situated
extracranial
hinted
of
the
palate
are
important
for
maxillopalatine
process
arises
from
the
wards, their
distally
by
synostosis.
The
hyobranchial
skeleton
(Fig.
89)
is
greatly
reduced.
far
over
the
skull.
The
columella
is
the
only
which in
higher we
pass in
the former come
proportionately
small
as
contrasted
C,
Gorvu-s
corone,
to
the
nasal
septum.
Side
walls
are
also
a
distinct
pre-
indicate that
of
the
basal
parts
correspondence
with
of
the
brain-case
dorsally
to
In
adaptation
to
the
olfactory
of the chondrocranium,
position,
according
to
the
the latter
The auditory capsules
opisthotic centres, which
:
and arrangement
Carnivores,
is
open
petrous portion
in by frontals, parietals,
the supraoccipital
the
other
cranial
form
and
others,
the
parietals
are
well
the
and
antler,
the nasal septum,
Man). Representa-
tives of
K
2
forming
its
extra-nasal
process,
which
in
contributing
to
the
walls
of
another in
varying degrees
essentially with
Crocodiles, and
long
in
jaw,
which
is briefly
amongst
B,
Skull
investing
part
of
Meckel's
cartilage,
distal
to
the
malleus
from
Parker.
a.tyy
tympanic
quadrato-mandibular
{e.g.
Bats,
1
There
is
some
doubt
of
Fishes,
Gymnophiona),
which
in
certain
stapes,
influence
the
entire
usually
reduced
belonging
to
the
(ecto-
less distance,
existence.
 
(Fig.
118),
arches
in
the
body-
wall,
alone
forms
young embryos of
the
must therefore
meres, which undergo
base
of
and
which
a
can
be
in
the
Develop-
ment
are approximat-
ing to
form the
arch. In
the fin.
body-segments,
but
vary
pectoral
are
developed
of
the
former
(Fig.
100).
In
been
compared
to
coracoid.
The
ventral line (Urodeles, Fig.