24 



EVENINGS AT THE MICROSCOPE. 



with angular ends (as represented in the accompanying 

 engraving). By transmitted light they are so transparent 

 and filmy as to be only just discernible ; 

 but by reflected light, and especially 

 under the sun's rays, they flash like 

 plates of polished steel. But what ap- 

 pears most singular, is that each spicu- 

 lum is perpetually vibrating and quiver- 

 ing with a motion apparently quite spon- 

 taneous, but probably to be referred to 

 slight vibrations of the water in which 

 spicula op gold-fish's they float ; and each independently of 

 scales. ^ res ^ so ag to convey the impres- 



sion to the observer that each is animated with life, though 

 the scale be taken from a fish some days dead. Owing to 

 this irregular motion, and consequent change of position, 

 each spiculum, as it assumes or leaves the reflecting angle, 

 is momentarily brightening or waning, flashing out or 

 retiring into darkness, producing a magic effect on the 

 admiring observer. To this property, I suppose, is to be 

 attributed the beautiful pearly play of light that marks 

 these lovely fishes, as distinguished from the light reflected 

 by an uniformly polished surface. I have found the pearly 

 pigment of the scales to be provided with similar spicula in 

 fishes widely differing in size, structure, and habits ; as 

 the Gudgeon and Minnow, the Pike and the Marine Bream. 

 The spicula of these fishes agree in general form with those 

 of the Gold-fish ; and also in size, with the exception of 

 trifling variations in the comparative length and breadth. 

 The colouring matter is lodged in lengthened cylindrical 

 cells, arranged side by side, and running across the scale ; 

 that is, in a direction at right angles to the lateral line. 



