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

130 F. H. Edgeworth -
arch there is, in young embryos (size not stated), an epithelial connection
between the pharyngeal epithelium and the skin which represents a sixth
gill-cleft. Again, on the left side of a 25 mm. Triton larva the Levator arcus iv
consisted of two portions, inserted (a) into the cartilage, and (b) into the
inscriptio extending back from it; whilst on the right side there was in addition
a Levator v inserted at the junction of the inscriptio tendinea and the ligamentum
branchio-pericardiacum. Between Levator iv and Levator v was
an epithelial connection between the epithelium of the pharynx and the
Plica omo-branchialis (which is formed from the fourth "Kiemenblattchen"
and the skin of the shoulder region). This lies at the position where a sixth
visceral-cleft would be expected and represents the remainder of it. The
position agrees with that found in Salamandra larvae.
In Siredon Levator arcus iv is inserted to Ceratobranchiale iv and an
inscriptio tendinea extending back from it. The Transversus ventralis arises
from ceratobranchiale iv, the inscriptio and the ligamentum branchio-pectorale.
Further, the fourth bronchial nerve gave off an inconstant sensory
branch which passed under the ligamentum branchio-pectorale, lying behind
the position in which-on comparison with Salamandra and Triton larvaethe
sixth gill-cleft is to be sought. This is a rudiment of a R. posttrematicus v.
Once a small epithelial vesicle was found which was regarded as the remains
of gill-cleft epithelium. Also a fine nerve was given off from the R. pharyngeus
of the fourth bronchial nerve, which was regarded as a R. pretrematicus vi.
There is thus in these larvae the remains of a sixth gill-cleft behind Ceratobranchiale
iv, and the Transversus ventralis has fourth and fifth bronchial
elements. In Triton there is also a Levator v. The laryngeal structurescartilage,
Dilatator laryngis, and laryngeal muscles-consequently do not
belong to a fifth bronchial segment, as Wilder, Gegenbaur and G6ppert supposed,
but to some more posterior segment, at least to a sixth, possibly to
one still further back.
Laryngo-tracheal skeleton
Anura. The laryngeal cartilages of Anuran larvae consist of a short rod
on either side of the larynx. The adult conditions have been described by
Henle and Wilder, and their development by Martens.
Gymnophiona. Goppert has described the condition of the laryngeal
cartilages in a late larva of Ichthyophis videe infra).
Urodela. The laryngo-tracheal skeleton of Urodeles consists of a continuous
or interrupted cartilaginous or fibro-cartilaginous rod on either side of the
larynx and tracheal.
1 pars trachealis cart. lat. is not present in Necturus where the short trachea is surrounded
by fibrous tissue only; it is present in other Urodela, cartilaginous in Siredon, Salamandra, Triton,
Ellipsoglossa and Proteus, fibro-cartilaginous with or without islands of cartilage in Menopoma,
Megalobatrachus max.,Amphiuma and Siren. It is continuouswith the pars laryngea in Menopoma,
Megalobatrachus max., Ellipsoglossa, Amphiuma, Siredon, Proteus and Siren. It is separated in
Salamandra and Triton (Driner).