REGULATION OF FORM - AND STRUCTURES 93
should be close together to begin
and inthe Çlupeids
we nd that the anterior portions arefused
line (Goodrich; 1920), forming @ coràcoid plate. In the
Plectognaths, as mentioned, the two bars are
their whole length ati—dinsome other forms, like Gastrosteus‘
and Monocentris, theyare closely appos€d
another,This may be considered the primitive condition, orareturn
to the primitive condition.
the greatmäxjority
the bars and c0racoid plates aré either worked
sides
or disappeañ ‘ Possibly the pelvic “bone in the- more
spedalised Teleosts is the real homologue of the…printivë
coracoid plate ; in which case the cartilage bones forming the
base of the pectoral n should really be called scapulars and
not coracÿids, as is usually done.
.
'
.
The-Ÿëfovâr-l 'of the pectoral ns up the sides may be
referred to thé'tendency of the body ‘to swing from; side to
_
Side Just1nthis region, and is more strongly markedin those
an anterior air—bladder or none_at _all‘.—_‘
'
_ï
_
In
Elasmobranchs the,—bases of the
spi‘éa‘d’well
out to the
f-"
=
—
'
,
‘
'
the
of shes ï have thus
arisen— frorñä the ventralis po$sible that they are in
no way homologous
Verte—'
,
Ï_h‘the
,
to have arisen'from an
as is indicated—both by itsPosition and.
.
_
"The peculiar m0de of development of the
the
frogs also points in the same direCtion;—
'
'
', -.
,
'
is also evidence that the position of the ventràl
ns -is' determined by the balance and movements of the
body. Where the ventral ns
=
abdominah they develop
just under'the expandedporti0n of the air-bladder, thus in 35
'
position of comparatiVe rest,
they mQŸ_Ôà
forvärards with the
and… the …anal n
‘
«
or diSappear.
,
;
The structure of
paired‘hs
,
”
same rules as the vertical
of the ns the Cartilaginous-basŒ
»