IIAd-KISIlKfS. 



1199 



partly enter into tlie eoiiiiiositiuii of tlic ton,i;ue, pMrfly 

 are intended f'oi' the locomotion in different directiotis 

 of tlie said organ, tiie mouth and nasal duet, and the 

 palate and branchial apparatus. These muscles consist 

 of striated fibiv. 



As for the bJaod-rasciilar si/stciii, tiie heart (tig. '^f)^) 

 is composed, as in other fishes, of an atrium, a \en- 

 tricle, and a tnmcKS arteriosits. Of the two Cuvierian 

 duets onl)- the left attains full development, and of the 

 two cardinal veins tlie right is feebly (U'velo|ied and 

 joins the left. The blood coming from tiie liind part 

 of till' body accordingly flows into the left Cuvierian 

 duct; the hepatic veins are discharged l)y two trunks 

 directly into the sinus renosiis. The portal vein, which 

 also receives tiie numerous ^•eins coming from the gene- 

 rative organs (mesovarium or mesorchium), dilates into 

 :i wide sac, the "portal heart" discovered by A. Ketzius, 

 before distributing itself to the two lobes of the liver. 



The bimpliatlc and serous system is strongly deve- 

 loped in Myxme. Under the greater portion of the 

 cutis there lies, throughout the dorsal region, fi-om the 

 snout to the tip of the tail, on both sides a. large (sub- 

 cutaneous) Ij'mph-space, which dorsall)' extends quite to 

 the median line, where a thin lamina of connective 

 tissue, |)rovided with nerves and bloodvessels, divides 

 the two lateral spaces, except in the cephalic region, 

 where thej' are in open communication Avith each other. 

 \entrally 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 pliarvnx, there lie more 

 profound Ivmph-spaces, which, according to Klinckow- 

 strom", are in open communication with the large sub- 

 cutaneous space; even the gill-sacs are furnished, accord- 

 ing to the same author, with l^^mph-sijaces. IJetween 

 these j)arts of tlie lymphatic sj'stein and the portal 

 heart, according to him, there apparently exists a com- 

 munication. He also describes a direct communication 

 lietweeii the vessels metamerically radiating in tiie tail 

 from the lateral (and "ventral") lymph-spaces and a 

 \essel running at the margin of the caudal cartilage 

 and "opening into the paired caudal heart discovered 

 by Retzu.s". This last-raentioned organ (tig. 354, f), 

 which has a certain resemblance to the pulsating organ 



long since observed in the Eel, ap])cars on each side 

 of tlie ventral lamella of the caudal cartilage, is fur- 

 nislied with spciial muscles, and exhibits quick, rhyth- 

 mical contractions; it is sanguiniferous and discharges 

 its contents directly into the vena caudalis''. Of interest 

 is the circumstance made known by Klinckowstkom 

 tiiat the subcutaneous lynq)h-s|)aces as a rule carr}' a 

 red fluid with a strong admixture of blood; the ex- 

 planation of this may well be supplied in part by the 

 above-mentioned coinmunications between the blood- 

 vascular system and the lymphatic system, but the 

 circumstances re(|nire further elucidation, for tlic l)urst- 

 ing of bloodvessels in conseipience of the usually 

 rapid transference of the animal from a great depth 

 may contribute to tiie said appearance. 



The skin, whicii owing to the large lym])h-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 bodj- as a rule somewhat shallower, more flat- 

 tened. No scale-growths can be traced in the skin. 

 Of gJandidar gnrwths in the same only the muciferous 

 glands so characteristic of the Myxinoids 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 bej'ond 

 the cloaca, back to the anterior end of the ventral la- 

 mella of the caudal cartilage (fig. 354, A-), though with 

 a break behind the cloaca (fig. 363, /;). 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 tine pore-like aperture, which apertures 

 lie in a line at a distance of 2 or 3 mm. from one 

 aiiotlier. These glands copiously secrete an extremely 

 tough, whitisli gray nunnis, whicli proves on microscopical 

 examination to consist of tine, strong threads, wiiich 

 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 Kunckowstr6m, Biol. Fiireningens Forh., Bd IV, Nos. 1 — 2. 1891. 



' G. Retzius, Ein s. g. Caudalherz bei Myxine glutinosa, Biolog. rntersucliungeii, N. V. I, 1890. 



