OF ARTS AND SCIENCES. 239 



tions. Now the most powerful microscopes show the lines, and they 

 have been photographed of every band by Dr. "Woodward in "Wash- 

 ington. But even now science is not entirely equal to mechanics, as 

 the photographs show by some optical illusion six or more lines than 

 were made by Mr. Nobert. Perhaps in the color-changing butterflies 

 natural colors are combined with optical colors, or perhaps interference 

 colors produced by superposed lamella; are combined with those pro- 

 duced by fine striae. It will be necessary to deprive the wings of 

 their natural colors by bleaching, and then to make a microscopical 

 examination. I have begun experiments for this purpose. The 

 wings of Apatura clytie, a variety of A. ilia, are pale yellow in the 

 color-changing part ; the wings of Euploea stiperba are velvety black 

 above, the black changing into violet in the color-changing part. 

 Both wings, put in eau de Javelle, began to grow pale after one hour. 

 The paleness began first in the color-changing part of E. siiperba, 

 and was less visible in the much lighter-colored wings of A. clylie. 

 After one hour and a half the whole color-changing part of both 

 species was entirely hyaline. The not color-changing parts were very 

 little affected, and in A. clytie the light-brown spots were nearly intact. 

 Both wings had lost entirely the change of colors. The microscopical 

 examination showed that the scales of the color-changing parts were 

 very much affected. The scales were hyaline, nearly invisible ; the 

 longitudinal stria? less sharp, the transversal ones even more affected, 

 and mostly obliterated. In some places in the middle of the color- 

 changing part the scales had disappeared, and only their stems were 

 left. On the other hand the scales of the not color-changing parts 

 were nearly unchanged, and both kinds of the stria; as sharp as before- 

 The under side of the wings does not change color at all, nevertheless 

 the parts corresponding to those iridescent ones of the upper side 

 were affected as much and in the same manner as the scales of the 

 upper side. From the beginning of the bleaching process both sides 

 made the same progress in becoming hyaline. Now the stria; of the 

 scales, though they had been much affected by the bleaching, could 

 not be the producers, at least not alone, of iridescence, as in all not 

 color-changing scales the stria; are exactly of the same arrangement 

 and distance, just as fine and approximate as in the iridescent ones. 

 Therefore it may be ^iresumed that the lamella; of the iridescent 

 scales are more distant one from the other, less firmly glued together, 

 and therefore easier affected by the bleaching fluid and the colored 

 substance between the lamellae easier bleached. But why are the 



