Mar., 1903 .] 
Spelerpes longicaudus. 
387 
the ceratohyal cartilage, just outside of the origin of M. hypo- 
branchialis, and sending its fibres inward to the extremity of the 
operculum. The function of the muscle is to raise the opercular 
fold and to create thus a suction through the gill slits. There is, 
of course, no homologue of this muscle either in Rana or in 
Cryptobranchus. 
M. Levator arcuum branchialium. — (Plate 11, Fig. 1, 
mla.) This slender and insignificant muscle arises as a fasciculus 
of M. longissimus dorsi. It is given off from that muscle at the 
extreme posterior end of the otic capsule and extends posteriorly 
and obliquely downward to an insertion on the first epibranchial 
bar. It serves to raise the branchial apparatus. 
M. Constrictor arcuum branchialium. — Plate 11, Fig. 3, 
mca., nice., mei.) This muscle is divided into three equal parts, 
which, from a common origin, separate and run to three distinct 
and different insertions. The muscle itself is a continuation or 
prolongation of the fibres of M. hypobranehialis, and takes its 
course along the inner or body side of the arches. Its first fasci- 
culus is inserted on the course of the second epibranchial cartil- 
age, its second fasciculus on the the third epibranchia and its 
third part along the course of the last arch. Its evident function 
is the closing of the branchial clefts, acting with M. cerato- 
branchialis to create a suction of water through the clefts. 
M. Depressor arcuum branchialium. — (Plate 11, Fig. 2, 
mdb.; Fig. 3, mab. ) This muscle is a sheet of fibres arising on 
the inner side of the last branchia and sending its fibres inward to 
mingle in the middle line. The main part of the muscle is just 
anterior to the tracheal opening, and some of its fibres even mingle 
with those of the following muscle. The name of the muscle 
indicates its function. 
M. Omoiiyoideus. — This is a rather small and insignificant 
muscle at this stage. It arises in the region of the future scapula 
and sends its fibres downward to mingle around the trachea. This 
muscle does not function before the metamorphosis, and as no sign 
of a scapula appears, it cannot now be traced to a definite origin. 
BODY MUSCLES. 
The two body muscles which appear at the present stage are 
the M. longissimus dorsi, and M. rectus abdominis. 
M. Longissimus dorsi. — (Plate 11, Fig. 1, mid., mli.) This 
large and important muscle has a double origin. The first is on 
the auditory capsule, on the dorsal side next to the surface, and 
in the region of the articulation of the jaw and of the eighth 
nerve. The second origin is considerably posterior to the first and 
is at the base of the brain, on the parachordal cartilages. From 
their origins, both fasciculi run directly tailwards, uniting in the 
region of the tenth nerve, to form a dumb-bell-shaped muscle 
which partially surrounds the medulla. After this point, the 
muscle rapidly increases in size, as it runs on back toward the tail. 
