MYXINES. 127 



flesh is much esteemed. The Fresh Water, or River Lamprey, 

 Petromyzon fluviatHis, \s a smaller species, seldom exceeding 

 eighteen inches in length, and passes the greater part of the 

 year in fresh water lakes, which it abandons in the spring to 

 enter rivers. Its colour is dark olive above, and yellowish or 

 silvery beneath. It is found in the fresh waters of New England. 

 A third species is the small River Lamprey, eight or ten inches in 

 length ; it also inhabits fresh waters, and is distinguished from the 

 preceding by its dorsal fins, which are continuous or united, 

 instead of being distinct. 



23. The Hag-jishes, Myxine have the maxillary ring entirely 

 membranous, and armed above by a single fang-like tooth, or they 

 are entirely destitute of teeth, while the tongue is armed on each 

 side with two horny plates deeply serrated, so that, at first sight, 

 they might be supposed to have lateral jaws, like articulated ani- 

 mals with which in fact, some authors have placed them ; in other 

 respects their organization is analogous to that of lampreys. Their 

 body is cylindrical, and furnished posteriorly with a fin which sur- 

 rounds the tail; their mouth is circular, surrounded by eight cirri, 

 and its upper margin is pierced by a spiracle which communicates 

 with its interior. They have no vestiges of eyes, and their body 

 is lubricated by a great quantity of mucus. Thus provided, the 

 Myxine, when it attacks its prey, uses its mouth like a cupping- 

 glass, and plunges its fang into its flesh ; and, thus securing a 

 firm hold, the lingual saws tear their way into its very vitals. 

 Some, called Heptatrennis, have seven branchial apertures on 

 each side of the neck; others, named Gastrobranchus, have on 

 each side, a canal, which receives, through particular holes, the 

 water coming from the branchia?, and empties externally by a 

 hole situated at about one third of the length of the body ; and 

 in others again, the branchial openings are arranged as in the 

 lamprey and heptatremus ; but the fleshy lip, which is unprovided 

 with teeth, is only semi-circular, and covers only the upper part 

 of the mouth which prevents them from using it as a means of 

 attaching themselves. These last myxines, which are named 

 rfmmocetes, have an entirely soft and membranous skeleton; they 

 keep in the mud of small streams, and have many of the habits 

 of worms, which they resemble also in form. 



It may be well for the reader, who has followed us through 

 our first, second, third, and fourth books, to remark that we 

 began our account of the animal world, with a general description 

 of the most perfectly organized being, and we found man, inde- 

 pendently of his possessing an immortal soul, the most complete* 



23. What are the characters of the Myxines ? 



