JlII. On certain Appearances observed in the Dissection of the 

 Eyes of Fishes. By James L. Drummond, M. D, 

 of Belfast Communicated by Dr Thomas Brown, Pro- 

 fessor of Moral Philosophy in the University of Edin- 



burgh* 



(Read 2d May 1814.^) 



SOME months ago, in investigating the anatomy of the eyes 

 of fishes, I washed off the back silvery part of the choroid 

 coat of the haddock, with a hair pencil, and about half a tea- 

 spoonful of water. The latter became of a milky colour, and on ex- 

 amining a drop of it, with an Ellis's aquatic microscope, I found 

 the milkiness to be owing to innumerable slender, flat, silvery 

 spicula, which had composed the substance of the choroid. 

 They seemed to be in constant motion, apparently rolling up- 

 on their axes, but having no degree of progressive movement. 

 The light reflected from their surface was very brilliant, like 

 that from polished silver, and often disappeared, and again re- 

 turned, with alternations so rapid, as to produce a twinkling, 

 very like that of a fixed star. 



Sometimes, on examining an individual specimen, it would 

 disappear altogether, but in a few minutes return, renew its 

 twinkling, and apparent revolution on its axis, and again dis- 

 appear, to return as before. 



Frequently 



