1202 
SCANDINAVIAN FISHES. 
The spinal cord consists of a flattened band, of 
uniform breadth and somewhat triangular in section, 
which in a fairly spacious medullispinal canal, lying on 
the notochord, follows the latter to its posterior termi- 
nation, and there extends in a contracted ependymal 
filum terminate somewhat behind the same (fig. 354,/). 
By means of improved colouring methods the form, dis- 
tribution, and processes of the ependymal as well as 
the neurogliar and ganglion cells has been elucidated on 
a fairly extensive scale in the spinal cord and partly 
too in the brain. 
The nerves originating in pairs, but not quite sym- 
metrically, from the spinal cord (spinal nerves) each 
have a ventral (motory) and a dorsal (sensory) root, 
and the latter is furnished with a ganglion. As in 
Petromy zon, all the nerve-fibres are “pale”, being with- 
out myeline sheath. The motory nerve-fibres end their 
terminal ramifications on the muscular fibres in free 
D- /’ c 
— 0 
A 
* 
... /XA, 
4 # 1 
h | 
.r" -if< 
f\V 0 
flAt 1 
. J ' ...'a?--- 
v ' 
i g d 
Fig. 360. Auditory organ of the right side of Myxine glutinosa , 
seen from above and within, X 18. 
a, internal division with e, the macula acustica; b, external division 
with an ampulla at each end (c, d) and a crista acustica (/, g ) in 
each ampulla; i, i, branches of the acoustic nerve; h, endolymphatic duct. 
“end-trees” within more or less marked end-hillocks 
(end-plates). The sensory fibres terminate within the 
different organs also in free intercellular ramifications. 
Such is the case too with the nerves in the epithelium 
of the skin and mucous membranes. No special sensory 
organs (end-cells, end-buds, sensory corpuscles, etc.) 
have been demonstrated. Even in the tentacles sur- 
rounding the oral and nasal apertures only free terminal 
ramifications of the sensory nerves in the epidermis 
have been traced, but here there is a slight sign of 
end-buds, round whose cells the nerve-ends ramify. 
No lateral line with appertaining end-buds appears either 
on the head or the body. In the subcutaneous nerve- 
plexus, on the other hand, especially in the head, nu- 
merous ganglion cells have been found embedded. Pos- 
sibly they belong to the sympathetic nervous system , 
whereof else no trace has hitherto been discovered. 
These ganglion cells further remind us by their po- 
sition in some degree of the cells in the rostral region 
of the Lancelet, close to the foremost nerve-pair. 
Of the organs of sense proper the olfactory organ 
is obviously the most powerfully developed. It forms 
(fig. 359, i ) a conical organ situated close before the 
brain in a cartilaginous basket and consisting of nearly 
vertical and dense folds of mucous membrane, their 
surface covered with olfactory epithelium, i. e. olfactory 
cells with supporting cells arranged between them. The 
filamentous, central processes of the olfactory cells enter 
the olfactory bulb, and- terminate there in numerous 
ramifications and with free ends in the olfactory glome- 
ruli, in which other nerve-fibres, from the ganglion 
cells (mitral cells) of the bulb, running towards the 
periphery, also terminate in free ramifications. The ol- 
factory organ of Myxine thus exhibits in the main the 
same structure as this organ retains throughout the 
whole of the vertebrates, even including man. Here 
there is no trace of “olfactory end-buds”, as Blaue 
has endeavoured to demonstrate in the Teleosts. Neither 
in the latter nor the Cyclostomes, nor indeed in any of 
the vertebrates, do such “end-buds” exist as Blaue 
meant; and his theory of the genetic connexion between 
the olfactory organ and the sense-organs of the skin, 
especially the lateral line, is therefore without ground 
in the structure of the said organs. 
Special organs of taste have not yet been demon- 
strated in Myxine, whereas Petromy zon and its larva dis- 
play within the mouth cavity bulbous or gemmiform 
organs that may with reason be regarded as represent- 
ing the gustatory organs of the higher vertebrates®. 
The organ of sight in Myxine 6 is very rudimentary. 
It is composed of the two very small, oblong eyes dis- 
covered by Johannes Muller, which, covered by the 
skin and a layer of muscles, lie on each side of the 
fore end of the brain (olfactory brain) and close to the 
posterior outer angle of the cartilaginous basket invest- 
ing the olfactory organ (fig. 359, h). The two optic 
° Cf. G. Retzius, Biol. Unters., N. Folge, Bd. V, p. 69, taf. XXVII. 
b Cf. „ , 1. c., p. 64, taf. XXVI. 
