on the development of the hypobranchial and laryngeal muscles in ...

144 F. H. Edgeworth
a lateral portion is separated from the anterior part and passes from the
Branchiale i to the Hyale; and Subarcuales recti iii and iv unite forming one
muscle. As regards Gymnophiona, in Siphonops larvae, where there is no
Basihyale, Subarcualis rectus i is single, whereas in Ichthyophis larvae, where
a Basihyale is present, Subarcualis rectus i separates into two muscles. In
Urodela, whilst Subarcualis rectus i remains single, considerable modifications
occur in the hinder subarcuales-probably associated with the backward growth
of the Genio-hyoid and the formation of a Urobranchiale. These chances are,
shortly, an insertion of Subarcuales ii and iii to the Urobranchiale directly or
indirectly, so that they form Subarcuales obliqui ii and iii (in Necturus and
Proteus ii only), and an extension forwards of the hindmost Subarcualis rectus
(fourth in Urodela with four bronchial bars, third in Necturius and Proteus) to
Branchiale i.
Transversi ventrales are formed by ingrowth from the ventral ends of the
bronchial muscle-plates. Transversus ventralis i is present only in Gymnophionan
larvae. Transversus ventralis iv (iii in Necturus and Proteus) is
formed in all Amphibian groups, though it is rudimentary and soon disappears
in Atiuran larvae; it spreads backwards, forming a broad sheet, which in
part or wholly underlies the respiratory tract.
Innervation of the ventral branchial muscles
Anura. The account given by Strong is not detailed, but he states that
the Recurrens does not spread into the bronchial region.
Gymnophiona. Norris and Hughes state that in Herpele (adult) the
Recurrens innervates the Transversus ventralis iv in addition to the laryngeal
muscles. In a 7 cm. larva of Siphonops, and in 3-5 and 5 9 cm. larvae of
Ichthyophis I find that the Recurrens innervates the same muscles as in
Herpele, i.e. it does not extend into the bronchial region nor does it innervate
the Subarcuales recti and Transversus ventralis i.
Urodela. Druner stated that Subarcualis rectus i is innervated solely
by the ix in Menopoma, Megalobatrachus max., and Necturus. It has an
additional nerve supply from the hinder bronchial nerve or nerves and the
Recurrens intestinalis in other Urodeles. Subarcualis obliquus ii in Necturus
is innervated by the second bronchial nerve, in Proteus by this and probably
also by the Recurrens. Subarcuales obliqui ii and iii in Ellipsoglossa and
Menopoma are innervated by the second and third bronchial nerves, in Megalobatrachus
max. and Siredon by these and the Recurrens, in Salamandra and
Triton by the Recurrens, in. Siren ii by the second bronchial nerve and iii
by the Recurrens. In Amphiuma the single Obliquus is innervated by the
second bronchial nerve and the Recurrens.
Subarcualis rectus iv is absent in the adult forms of Ellipsoglossa, Megalobatrachus
max., Siredon, Salamandra and Triton; in Menopoma (adult) a and b
are innervated by the second and third bronchial nerves, c by the fourth
bronchial nerve and the Recurrens; in Siredon (adult), Amphiuma (adult),