1200 
SCANDINAVIAN FISHES. 
about 1 cm. behind the branchial apertures, where 
there appears a fold triangular in section, thus with 
broad base and as a rule with the free flap measuring 
only about 2 — 3 mm. in height, which fold may be 
regarded as representing a ventral fin. 
No external limit is visible between the body and 
the head. The tip of the snout terminates dorsally in 
a median triangular dermal flap; underneath this is the 
slit-like oval nostril (fig. 363, /), flanked on both sides 
by two (thus altogether four) conical, pointed tentacles 
(papillae) about 3 mm. long and directed forwards and 
somewhat upwards. These contain in their axial part 
the above-mentioned small cartilaginous rods (fig. 355, m ) 
and are covered with soft skin. Under the tip of the 
snout the anterior surface of the head slopes backwards 
and downwards, and 7 — 8 mm. behind the tip of the 
snout opens the oral aperture (fig. 363, m), its appear- 
ance varying with its functional position. In its su- 
k o 
Fig. 357. Sagittal section of the cephalic end of Myxine glutinosa, X 4. 
a, month aperture; b , nostril; o, nasal duct; d, connecting canal be- 
tween the nasal duct and the pharynx; e, pharynx; f, nasal tentacles; 
cj, oral tentacles; li , olfactory organ; i, olfactory lobe; k, forebrain; 
Z, ganglion habenulae; m, midbrain; n, hindbrain (little brain) ; o, cen- 
tral ventricle ; p , afterbrain (medulla oblongata) ; q, myelon ; r, dorsal 
muscular layer; s, medullispinal canal; u , notochord. 
perior margin may usually be seen, when it is retracted, 
two large and two small folds of skin and in its inferior 
margin several small folds of a somewhat variable na- 
ture. Suctorial mouth or sucking-disk, like those of 
Petromyzon , there is none; nor are there any true lips. 
On the other hand, both sides of the oral aperture are 
furnished in Myxine with two, thus altogether four ten- 
tacles (papillae) of a similar kind to those situated round 
the nostril. Of these tentacles the inner pair (situated 
nearer the mouth) are small and broad; the other pair, 
set outside and somewhat above the former, are longer, 
narrower, and more pointed. The irregularly slit-like 
(“stelliform”) mouth, open only when the animal is 
eating, leads into a long buccal cavity, dilating behind, 
in the roof of which, about 1 cm. behind the tip of 
the snout, is a somewhat crooked horny tooth with 
retral tip. This tooth, surrounded by folds of mucous 
membrane, is attached to the ethmoid cartilage and is 
therefore called the ethmoidal tooth (fig. 355, lit). A 
few millimetres further back (13 — 14 mm. behind the 
tip of the snout), viz. when the tongue is in its normal 
position of rest, lie the supralingual teeth (fig. 356, d), 
attached to the upper surface of the tongue (to the 
supralingual cartilage) and arranged in anteriorly con- 
vex, approximately concentric curves; these are also 
horny, and their tips are directed backwards and in- 
wards. When the tongue is protruded, this dental 
apparatus is visible at the oral aperture. Above and 
behind the same opens the above-mentioned tubiform 
nasal duct (fig. 357, c ) through a canal (d) sloping 
downwards and backwards in the palate, and further 
back appears a fold of mucous membrane at the tran- 
sition to the pharyngeal tube, which ( e ) runs straight 
back above the long tongue-apparatus to pass behind 
the branchial apparatus, in the form of an also com- 
paratively narrow and long “oesophagus”, into the in- 
testinal canal. This (fig. 363, e, f) has the form of 
a straight, thick-walled, broad and capacious tube, 
furnished internally with shallow, longitudinal, zigzag 
folds, but without “spiral coils”, and runs to a point 
distant about 3 — 4 cm. from the tip of the tail, where, 
after bending downwards (ventrally), it opens into the 
cloaca , situated in the median line and nearly 1 cm. 
long, which terminates in a sagittal slit, the outer 
cloacal aperture (i), flanked by two dermal flaps or lips. 
The gall-bladder duct enters the foremost part of 
the intestine. The gall-bladder lies between the two 
widely separated lobes of the liver (fig. 363, d) and 
receives a duct from each of them. Of pancreas and 
spleen not a trace has yet been found. The kidney of 
Myxine exhibits, as Johannes Muller, in his famous 
work on the Myxinoids, first showed, a very remarkable, 
extremely low development (“pronephron”); on each side 
of the notochord runs a duct opening into the cloaca 
and receiving during its course in the abdominal cavity 
a number of lateral branches, whose capsule-like dilated 
ends each contain a plexus of vessels, a glomerulus 
composing a branch of the aorta. 
In consequence of the powerful development of the 
tongue the branchial apparatus (fig. 358) is removed 
far back. It is not furnished with any branchial basket 
