IIAG-FISHE8. 
1199 
partly enter into the composition of the tongue, partly 
are intended for the locomotion in different directions 
of the said organ, the mouth and nasal duct, and the 
palate and branchial apparatus. These muscles consist 
of striated fibre. 
As for the blood-vascular system , the heart (fig. 358) 
is composed, as in other fishes, of an atrium, a ven- 
tricle, and a truncus arteriosus. Of the two Cuvierian 
ducts only the left attains full development, and of the 
two cardinal veins the right is feebly developed and 
joins the left. The blood coming from the hind part 
of the body accordingly flows into the left Cuvierian 
duct; the hepatic veins are discharged by two trunks 
directly into the sinus venosus. The portal vein, which 
also receives the numerous veins coming from the gene- 
rative organs (mesovarium or mesorchium), dilates into 
a wide sac, the “portal heart” discovered by A. Retzius, 
before distributing itself to the two lobes of the liver. 
The lymphatic and serous system is strongly deve- 
loped in Myxine. Under the greater portion of the 
cutis there lies, throughout the dorsal region, from the 
snout to the tip of the tail, on both sides a large (sub- 
cutaneous) lymph- space, which dorsally extends quite to 
the median line, where a thin lamina of connective 
tissue, provided with nerves and bloodvessels, divides 
the two lateral spaces, except in the cephalic region, 
where they are in open communication with each other. 
Ventrally the space extends close to the row of muci- 
ferous glands that runs on each side of the body. But- 
on the ventral side" there is no similar, large and con- 
tinuous lymph-space, only a- fairly abundant and dense 
subcutaneous connective tissue. In the head, however, 
especially around the tongue and pharynx, there lie more 
profound lymph-spaces, which, according to Klinckow- 
Strom 0 , are in open communication with the large sub- 
cutaneous space; even the gill-sacs are furnished, accord- 
ing to the same author, with lymph-spaces. Between 
these parts of the lymphatic system and the portal 
heart, according to him, there apparently exists a- com- 
munication. He also describes a direct communication 
between the vessels metamerically radiating in the tail 
from the lateral (and “ventral”) lymph-spaces and a 
vessel running at the margin of the caudal cartilage 
and “opening into the paired caudal heart discovered 
by Retzius”. This last-mentioned organ (fig. 354, c), 
which has a certain resemblance to the pulsating organ 
long since observed in the Eel, appears on each side 
of the ventral lamella of the caudal cartilage, is fur- 
nished with special muscles, and exhibits quick, rhyth- 
mical contractions; it is sanguiniferous and discharges 
its contents directly into the vena caudalis 6 . Of interest 
is the circumstance made known by Klinckowstrom 
that the subcutaneous lymph-spaces as a rule carry a 
red fluid with a strong admixture of blood; the ex- 
planation of this may well lie supplied in part by the 
above-mentioned communications between the blood- 
vascular system and the lymphatic system, but the 
circumstances require further elucidation, for the burst- 
ing of bloodvessels in consequence of the usually 
rapid transference of the animal from a great depth 
may contribute to the said appearance. 
The skin, which owing to the large lymph-spaces 
on the greater part of the body is free and moveable, 
consists of a rather thick, fibrous cutis and a super- 
incumbent epidermis, which is composed of several 
layers of polygonal nucleated cells, towards the surface 
of the body as a rule somewhat shallower, more flat- 
tened. No scale-growths can be traced in the skin. 
Of glandular growths in the same only the muciferous 
glands so characteristic of the Myxinoicls are known. 
These are set in a single row on each side of the belly, 
to a number of more than a hundred; the foremost 
(fig. 363, g) are situated behind the head (2'5 — 3 cm. 
from the tip of the snout); the hindmost extend, in oppo- 
sition to what is sometimes stated, a good way beyond 
the cloaca, back to the anterior end of the ventral la- 
mella of the caudal cartilage (fig. 354, k ), though with 
a break behind the cloaca (fig. 363, h). In form they 
are oval, and consist of sacs about as large as hemp- 
seed, lying under the skin and opening on its surface 
each at a small fine pore-like aperture, which apertures 
lie in a line at a distance of 2 or 3 mm. from one 
another. These glands copiously secrete an extremely 
tough, whitish gray mucus, which proves on microscopical 
examination to consist of fine, strong threads, which 
have lain rolled up in the secretory cells of the glands 
and been formed of the protoplasm within those cells. 
True fins there are none, but in the median line 
the skin forms folds, partly in the caudal region, where 
the fold contains the rays of the caudal cartilage and 
thus to a certain degree represents a caudal fin, and 
partly on the belly, from the cloaca forward to a point 
“ Axel Klinckowstrom, Biol. Foreningens Forh., Bd IV, Nos. 1 — -2, 1891. 
b G. Retzius, Ein s. g. Caudalherz bei Myxine glutinosa, Biolog. Untersuchungen, N. F. I, 1890. 
Scandinavian Fishes. 
151 
