Royal Microscopical Society. 249 



caution is especially necessary ere embracing new opinions on the 

 structure of minute more or less transparent bodies, however refined 

 may have been the method of investigation, if they be not fully sup- 

 ported by analogy in objects of the same nature, which permit of 

 more easy examination, and certainly it becomes imperative when 

 fresh research tends to opposite conclusions. 



By these prehminary remarks it is not intended to convey 

 the idea anyone should remain satisfied with the knowledge already 

 gained, but simply not to be too ready to accept evidence on a scanty 

 basis which for various reasons is open to considerable doubt. 



All acknowledge the manifold difficulties that supervene on at- 

 tempting to decide the structural nature of minute transparent 

 objects, when they are replete with optical eflfects, resulting from the 

 transmission of light, at vaiying angles, through irregular surfaces 



/, The focus, only, altered, giving rise to dark, elongated areas — 

 " notes," supported on a pale membrane marked transversely ; 

 the heads not rounded, but somewhat acute at one comer, very 

 like the appearance figured in ' Quekett on the Microscope,' 

 plate viii., fig. 4, a ; and some of the notes in Dr. Woodward's 

 photographs just received. 



<7, The position of the scale and incident light altered ; an appearance 

 approaching the first focus, but with two dark shadows, inter- 

 rupted, either side of the long rib ; the transverse markings 

 still seen. 

 i. The scale and direction of the light slightly changed, furnishing 

 dark shadows and highly chromatic effects (seen in the coloured 

 drawing), with universal faint striation. 



h, The appearance of a framework similar to the Lepidoptera scales, 

 seen with difliculty, and when the light is not thrown sufliciently 

 obliquely to produce colour — all magnified 2625 diam. 



The central portion of the figure gives the optician's view, 

 but showing oblique lines faintly. 



[The remaining figures refer to some exquisite photographs and 

 figm-es which have been placed by Dr. Maddox in the Society's 

 Collection.— Ed. ' M. M. J.' J 



Fig. 27. — A photograph of interference image of Fig. 31, produced by artificial 

 means ; simulating beads. 

 „ 28. — A photograph of the same artificial construction, using I plate lenses ; 



simulating Degeeria domestica scale. 

 „ 29. — A photograph i^uruishing bright beaded spots, dark shadow and coales' 



cence of the ribs. 

 „ 30. — A photograph showing faintly to the left (very distinctly in the negative) 

 a chain of dots (? beads) and the general image as a composed or 

 intermediate one between Figs. 28 and 29. 

 „ 31. — The rough pencil sketch of Fig. 15, used to construct the artificial framing. 

 „ 32. — Pencil sketch of injured scale of Hmnming-bird Sphinx (recent), 

 rt. The edge bars are rubbed into wavy lines. 

 6, Tlie external coat removed, 

 c, The little round particles of which the coat consists are rubbed 



into a confused mass, 

 c/, The surface seen in its natural state ; the round particles are most 



clearly seen on the bars, but they entirely cover the surface. 

 e, The quill is seen as a hollow tube. 



(Fig. and description by Dr. A. Southby, Italy.) 



