It is not improbable that the increased density and opacity 

 of the cornea here described may be one of the effects of in- 

 flammation produced by some of those numerous very minute 

 leech-like animals, which M. Nordmann has found to occur 

 so frequently in the aqueous humours of the eyes of fishes.* 



Two Continental naturalists have pointed out the neces- 

 sity of attending to the scales of fishes, as affording the most 

 valuable and constant characters ; and these productions of 

 the skin, important also as the organs of protection and rela- 

 tion between the animal and the medium in which it resides, 

 will occasionally be figured and referred to as additional 

 marks of specific distinction in several instances of closely 

 allied species. It has already been observed that the lateral 

 line in fishes marks the situation of an extended series of 

 mucous orifices. The scales placed in a row immediately 

 upon this lateral line mark its particular course along the 

 side ; and these scales, besides bearing the characters of those 

 of the other parts, are perforated by a tube through which 

 escapes this mucus, or slime, as it is more commonly called, 

 to be spread over the surface of the body. The vignette 

 below represents a scale from the lateral line of the Perch, 1 

 the Basse, 2 and the Ruffe. 3 



Influenced by the recommendation of several friends whose 

 opinions I defer to, I intend to introduce as vignettes the 

 crania of various genera of fishes from the works of Chesel- 

 den, Cuvier, Meyer, Rosen thai 1, and others, on the plan 



* Mikrographische Beitriige zur Naturgeschichte der wirbellosen Thiere von 

 Dr. Alexander v. Nordmann. Berlin, 1832. 



