108 FISHES AND nSHING. 



viscid slime, -which is supplied by ducts placed upon 

 their sides; in some fish this is more abundant than 

 in others ; some have these ducts placed pretty regu- 

 larly over the surface ; the mucus exuding from these 

 ducts is so extremely viscid that it is difficult to squeeze 

 it out." "Now as the scales of fish must have some 

 origin, is it not reasonable to think that tliis mucus, 

 after the more fluid portions have lubricated the sur- 

 facp, the remainder may solidify and form continually 

 the increasing number of laminae ? 



The anatomical formation of the eye in fish is a 

 most extraordinary proof of the exquisite and won- 

 derful adaptation of the parts of the animal to the 

 medium in which it is destined to exist, hence the 

 crj^stalline lens is quite round, which is not the case 

 with terrestrial beings; but from the conformation of 

 the whole apparatus, and the element in which they 

 exist, fishes cannot see objects far distant, though 

 some species, such as fish of pvej, have greater powers 

 of vision than others. As fish do not require any 

 aqueous secretion to keep the surface of the eye moist, 

 they have no lachrymal gland. Fish generally have 

 DO eyelids, some have a compensation for it, in a 

 species of fijced covering at each angle, very evident 

 in salmon and mackerel ; the eel too, to protect his 

 eyes in working his way through mud, has a trans- 

 parent case placed a little way before the eyes, of 



