ii9(; 



SCANDINAVIAN FISHES. 



Of thi; latter genus too three species have been 

 distinguished, respectively from the North Atlantic, the 

 Pacific Ocean (Sea of Japan), and tlie extreme south 

 of South America. 



As the Scandiiia\ ian fauna, however, contains only 



one representative of the Myxinoid family, namely 

 Myxine glntinosa, our principal attention shall be con- 

 fined Ix'low to this species, which has besides in re- 

 cent times been the most fretjuent subject of investi- 

 gation, and whose structure is therefore best known. 



Gems myxine. 



On each -s/rfc of tlic forepart of tlir bot/i/ (thf tliroat) a siriffh- bratichial ajierfinr, at irhich tlie duds /;iren out 

 hy the six qiU-sacf: of each half of the tioi/i/. after loiitiiiq hito a eommoii duct, fnd av outlet. 



In Mi/xhie, as in Fetromyzoii, the cj'lindrical noto- I a dorsal and a ventral lamella, which are confluent 

 chord, continuous, unsegmented, persists throughout Ijehind and form round both .sides of the termination 

 life, anteriorly terminating in a conical tip at the ba.sis j of the spinal cord a more or less narrow, short canal. 



Fig. 354. Caudal cartilage of ^fl/a)lu ijlutmusa. seen from tlit right, X 7. 

 a, ventral plate of the caudal cartilage; /;, 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; /), free dorsal and !, free ventral cartilaginous rods 



of tlif caudal fin; h. dermal muciferons ejlands. 



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 witli 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, 

 \\hicli does not differentiate, however, into any true 

 vertebral skeleton. Only at the head and tail are 

 cartilages developed, but in Myxhie they never assume 

 anj' vertebrally segmented character. Tims in the tail 

 (fig. 354, a) we find a median cartilaginous plate with 



The outer edges of this cartilaginous plate send out 

 upwards, back^\ards, and do\\nwards a great number 

 of slender cartilaginous rods {h), 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- 

 lagiiKius plate there appears in the caudnl fin, aliovc 

 and below, a scries of similar rods, the jjroximal ends 

 of whicli terminate in a button-like form within the 

 septum of connective tissue and are imjoiiied by cartila- 

 ginous tissue (fig. 354, /;, /). In Mjixive there is not 

 a sign, as in l'etromyz(i)i, of lateral cartilaginous arches, 

 to re])resent vertebral apo|)h3'ses. 



