CHONDROPTERYGII. G55 



conformation of the mouth. They are in general very lively, 

 and exude a considerable viscosity from all parts of their 

 body. Most of this .family inhabit the sea and the larger 

 lakes, but these ascend the rivers in the breeding season. 



All the species of this family want a swimming bladder, 

 consequently they all fall to the bottom of the water as 

 soon as they cease to move in it ; but as a compensation 

 for this, they have various means in most of the genera of 

 fixing themselves, so as not to be driven along by the current. 

 Thus the lampreys attach themselves on solid bodies at the 

 bottom of the water, by means of a sucker formed by the 

 mouth, the Myxine, by means of a moveable crook on the 

 upper lip, fasten on fish and suck their blood, but the Amo- 

 ccetes which in structure come nearer to the worms, cannot 

 even do this, and avoid their enemies only by suddenly 

 burying themselves under the sand or mud. 



All the Sucking-fishes feed on animal matter, either living or 

 dead. Many of them are blind. 



So much do these animals deviate from the ordinary cha- 

 racters of fish, that some naturalists have even hesitated 

 whether to associate them with this class, or to refer them to 

 the worms. Instead of a true vertebral column, they have a 

 cartilaginous trunk, of a single piece, which is observed to 

 soften at certain periods of the year. They have no articu- 

 lated members. Many of them, always blind, attach them- 

 selves like leeches to fish, to suck their fluids. None of 

 them possess horizontal moveable jaws. All have the intes- 

 tinal canal simple, and often without a mesentery. Their 

 respiration is effected by a single orifice. The ovary of the 

 female is situated in the same cavity as the intestines, united 

 in a single bunch, and the eggs do not pass through any 

 oviduct. 



The instruments of prehension and mastication in the first 

 two genera are moreover very like those of several annelida, 



