48 Transactions of the 



II. — Beport on Slides of Insect Scales. Sent to the Eoyal 

 Microscopical Society by the Chevaliee de Cerbecq, accom- 

 panied by a letter. Examined by Henry J. Slack, Sec. 

 E.M.S. 



(Read be/ore the Royal Microscopical Society, Jan. 3, 1872.) 



The objects on slides sent by the Chevalier appear to be mounted 

 in balsam, by which many are rendered so transparent as to require 

 great care in illumination. His intention in forwarding them was 

 to show that they confirmed the idea that a beaded structure was 

 a reahty, and not a mere optical illusion. On several slides the 

 scales are an-anged in star patterns, so that an illuminating ray 

 from any direction will fall upon them at difierent angles. 



The following examinations were made with PoweU and Lea- 

 land's new ith, Koss' C eye-piece and x%ths condenser, stopped to 

 an angle of 75", and employed with a single radial slot giving uni- 

 lateral light, generally sent across a scale nearly at a right angle 

 to its long axis. 



? Deilephila Elpenor (Elejihant hawk-moth) exhibits various 

 appearances according to illumination and focussing. An aspect of 

 coarse beads is evidently an optical illusion, and even if the 

 objective is well corrected, a false appearance is seen if the focussing 

 is too near the object. The most probably correct view seemed 

 that of longitudinal ribs, with trough depressions between them, 

 each trough crossed thickly with very numerous rows of beads in 

 fine lines. A false aspect is presented if these horizontal beads are 

 not well displayed. 



Melanippe. — 1. A scale showing better than most, gave 

 appearances somewhat similar to the preceding, but the bead rows 

 between the ribs inclined to be convex. This was not the case in 

 some other scales. Some scales appeared to contain a great many 

 more beads than others. In injured scales some bead rows were 

 displaced without injury, but in some spots which looked crushed 

 — no structure visible. Many scales show beading as plain as 

 possible. The fineness of the beading varies in different scales. 



2. Delicate beaded ribs, transverse rows as if in depressions ; 

 very distinct. 



MoRPHO Helinor. — Structure much the same. Beading very 

 delicate and fine, but beautifully sharp and clear. 



MiCROLEPiDOPTER. — Kibs not as strong as in most others. 

 Beading very delicate ; linear on some scales, in others running in 

 curved and angular directions to perpendicular axis. Beads very 

 distinct, though small. 



