.502 APPENDIX. 



into which selenite plates may be fitted, so as to be revolved 

 as occasion may require. 



SCALE OF AMATHUSIA HORSPIELDII. 



Through the kindness of Mr. De la Rue, the author is 

 enabled to furnish his readers with plate x., in which is a 

 representation of one of the characteristic scales of this 

 butterfly, as seen under a power of 825 diameters. The 

 following account of the structure of this scale has been 

 given by Mi". De la Rue, in vol. iii. of The Transactions of 

 the Microscopical Society : — 



" The outline of fig. 1 was first made with a power of 250 

 diameters, and by means of proportional squares enlarged to 

 the size corresponding to the magnifying power produced by 

 the twelfth ; a scale of thousandths of an inch being set off 

 with the camera in each case, to afford the standard of 

 comparison. The drawing was then corrected in detail, by 

 portions set off with the higher power, which were found to 

 match the enlarged drawing with tolerable accuracy ; in this 

 way a very fair representation of the scale and its markings 

 was produced. The cross striae, when viewed with a twelfth 

 of a lip° apertiu-e, and illuminated with a quarter of 60°, 

 used as an achromatic condenser, and adjusted well to focus, 

 came out under a power of 825 diameters in beaded lines, on 

 which protuberances were distinctly seen ; these latter, when 

 focused at their summits, appeared as brown dots. The 

 longitudinal strias, under the same circumstances, have like- 

 wise a somewhat corrugated appearance, but not so marked, 

 and at the upper surface similar dots. In fig. 2 is represented 

 a portion of the striee at the lower focus, as seen with a power 

 magnifying nineteen-hundred diameters, though the drawing 

 is made, for convenience, to a scale of forty-four-hundred to 

 one. The scale, when viewed from the under side with this 

 power, exhibits the lower membrane as slightly undulating, 

 probably from its being dry. 



" Some persons have thought that the constricted appear- 

 ance of the cross striae, just described, is due to the overlaying 



