1196 
SCANDINAVIAN FISHES. 
Of the latter genus too three species have been 
distinguished, respectively from the North Atlantic, the 
Pacific Ocean (Sea of Japan), and the extreme south 
of South America. 
As the Scandinavian fauna, however, contains only 
one representative of the Myxinoid family, namely 
Myxine glutinosa, our principal attention shall be con- 
fined below to this species, which has besides in re- 
cent times been the most frequent subject of investi- 
gation, and whose structure is therefore best known. 
Genus MYXINE. 
On each side of the forepart of the body ( the throat) 
by the six gill-sacs of each half of the body , i 
In Myxine , as in Petr omy son, the cylindrical noto- 
chord, continuous, unsegmented, persists throughout 
life, anteriorly terminating in a conical tip at the basis 
a single branchial aperture , at which the ducts given out 
if ter uniting into a common duct , find an outlet. 
a dorsal and a ventral lamella, which are confluent 
behind and form round both sides of the termination 
of the spinal cord a more or less narrow, short canal. 
a , ventral plate of the caudal cartilage; b , ventral cartilaginous rods (fin-rays) issuing therefrom; c, right sac of the caudal heart; d , button- 
shaped process of the ventral plate; e, notochord; /, spinal cord; g , medullispinal canal; h, free dorsal and i, free ventral cartilaginous rods 
of the caudal fin; k, dermal muciferous glands. 
cranii, under the brain, posteriorly extending close to 
the tip of the tail and terminating there after gradual 
contraction but somewhat obtusely, before the posterior 
extremity of the spinal cord (fig. 354, e). This noto- 
chord, composed of large cells filled with a clear fluid 
and cemented together by their investing membranes, 
is enveloped in two closely fitting sheaths, which have 
been somewhat differently interpreted by morphologists. 
These are surrounded by fibrous connective tissue, 
which does not differentiate, however, into any true 
vertebral skeleton. Only at the head and tail are 
cartilages developed, but in Myxine they never assume 
any vertebrally segmented character. Thus in the tail 
(fig. 354, a) we find a median cartilaginous plate with 
The outer edges of this cartilaginous plate send out 
upwards, backwards, and downwards a great number 
of slender cartilaginous rods ib), pointed at the tip, 
which compose the supporting rays of the caudal fin, 
and not without reason have been compared — or at 
least regarded as analogous — to the spinous processes 
of higher vertebrates. Even in front of the said carti- 
laginous plate there appears in the caudal fin, above 
and below, a series of similar rods, the proximal ends 
of which terminate in a button-like form within the 
septum of connective tissue and are unjoined by cartila- 
ginous tissue (fig. 354, h, i). In Myxine fhere is not 
a sign, as in Petromyzon , of lateral cartilaginous arches, 
to represent vertebral apophyses. 
