PETROMYZONID.E MYXINID-E. 77 



and which is the principal instrument in the act of suction, is 

 also furnished with two longitudinal rows of small teeth. By 

 means of this sucker, the Lamprey is said to attach itself to the 

 bodies of the largest fishes, so as speedily to pierce through their 

 integuments, and prey upon their substance. It seems far more 

 probable, however, that the Lampreys feed entirely upon small 

 aquatic animals. The largest species, which attain the length 

 of two or three feet, are marine ; the smaller, which chiefly in- 

 habit rivers, are sometimes called Lamperns. According to some 

 recent researches of Dr. August Miiller, the young of the Lam- 

 preys are very different in structure from their parents, being 

 in fact the Fishes described by Ichthyologists as forming the 

 distinct genus Ammoccetes. The most singular circumstance 

 revealed by his observations is that the Ammoccetes do not gra- 

 dually acquire the mature characters during their growth, but 

 first attain the full size of the adult Lamprey, and then pass 

 through a rapid change, so as to resemble the larvae of Insects. 



641. The members of the family MYXINIDJE, or Hags, have 

 not even a cartilaginous ring around the mouth, its borders being 

 entirely membranous, and furnished with only one tooth. The 

 mouth is surrounded by eight cirrhi, or tendril-like feelers ; 

 which remind us of the arms of the Cuttle-fish in miniature. 

 This fish is destitute of eyes ; and does not seem, indeed, to have 

 any other special organ of sensation than these cirrhi. The 

 commonest species is known to British fishermen under the name 

 of the Hag; it is found in the interior of other fishes, whose 

 bodies it has entered for the purpose of devouring them ; and it 

 seems to attack in preference those which have been hooked, 

 and which, consequently, are not able to defend themselves. As 

 many as six Hags have been found in the skin of a single Had- 

 dock on the Norway coast (where this species is more abund- 

 ant than on our own), the flesh of which they had almost entirely 

 consumed. It is usually from twelve to fifteen inches in length, 

 and of the thickness of the little finger ; and its whole tissues 

 are so soft, that it would not have been supposed capable of in- 

 flicting any serious injury. The quantity of mucus which it can 

 secrete from its surface is enormous ; it has been asserted, that 



