1200 



SCANDINAVIAN I-ISIIKS. 



about 1 ciu. behind tlie Ijraiicliial aj)ertures, where 

 there appears a fold triangular in section, thus with 

 broad base and as a rule with the free flap measuring 

 only about 2 — ?> mm. in lieight, which fold may be 

 regarded as representing a rontral fin. 



No external limit is visible l)etweeii the body and 

 the head. The tip of the snout tc-rminates dorsally in 

 a median triangular dermal flap; nnderneath this is the 

 slit-like oval nostril (fig. 3(38, I), flanked on both sides 

 by two (thus altogether four) conical, pointed tentacles 

 (papillae) about 8 mm. long and directed forwards and 

 somewhat upwards. These contain in their axial part 

 the above-mentioned small cartilaginous rods (fig. 35.5, 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 cif Myxine glutiiwsa, X 4. 

 a, niouth aperture; i, nostril; c, nasal duct; d, connecting canal be- 

 tween the nasal duct and the pharynx; e, pharynx;/, nasal tentacles; 

 I/, oral tentacles; /(, olfactory organ; i, olfactory lobe; k, forebrain; 

 /, ganglion habenulie; 7H, midbrain; ;i, hindbrain (little brain); o, cen- 

 tral ventricle; p, afterbrain (medulla oblongata); 7, myelon; )■, dorsal 

 irniscular layer; s, mcdullispinal canal; «, nntocliord. 



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 somewliat varialile na- 

 ture. Suctorial mouth or sucking-disk, like those of 

 Pefromi/znn, there is none; nor are there any true lips. 

 On till' other hand, both sides of tlie oral aperture are 

 furnished in Mij.cine with two, thus altogether four ten- 

 tacles (papillffi) 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 int<; a long buccal cavity, dilating behind, 

 in the roof of which, about 1 cm. behind the tip of 

 the snout, is a somewliat crooked horny tooth with 

 retral tip. This tooth, surrounded by folds of mucous 

 membrane, is attached to the ethmoid cartilage and is 

 th(n'efore called the ethmoidal tooth (fig. 355, hi). A 

 few millimetres fin-ther back (13 — 14 mm. behind the 

 tip of the snout), viz. when the tongue is in its normal 

 position of rest, lie the sirpralhif/ual teeth (fig. 356, d), 

 attached to the upper surface of the tongue (to the 

 supralingnal cartilage) and arranged in anteriorly con- 

 vex, a])[)roximately concentric curves; these are also 

 horny, and their tips are directed backwards and in- 

 wards. When the tongue is protruded, this dental 

 a])paratus is visible at the oral aj)erture. 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 coiu- 

 paratixcly narrow and long "lesophagus", into the in- 

 tesfiiKd ((DHd. 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, whicii terminates in a sagittal slit, tlie outer 

 cloacnl aperture (i), fianked by two dermal flaps or lips. 



Tlie f/all-hladder 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 ot 

 Mi/xine exhibits, as Johannes Mii-lek, in his famous 

 work on the Mj'xinoids, first showed, a very remarkable, 

 extremely low development ("pronephron"); on each side 

 of the notochord runs a duct o))ening 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 con.sequence of the powerful develoj)meiit of the 

 tongue the branchial apparatus (fig. 358) is removed 

 far back. It is not furnished with any branchial basket 



