472 MANIPULATION. 



Scales of Lepisma Saccharina. — These are so easily made 

 out by the lowest powers, that they can hardly be called 

 by the name of tests. Figs. 8 and 9, in plate ix., represent 

 two of the scales magnified 500 diameters ; the longitudinal 

 striae appear to stand out in bold relief, like the ribs on a shell ; 

 they are smallest at the lower part of the scale, and increase 

 in breadth, and become more prominent as they proceed to- 

 wards the outer margin ; a good glass should define well the 

 contrast between the strise and the interspaces. 



Scales from the Gnafs Wing. — Two of these are represented 

 by figs. 1 and 2, in plate viii. ; when magnified 500 diameters, 

 they exhibit very bold longitudinal bands or striae, which pro- 

 ject beyond the end in the form of spines; in the membrane, 

 between the longitudinal strife, there is sometimes an appear- 

 ance like the watering of silk; if one of these scales be viewed 

 with a J^ of 90° aperture, numerous striae wiU be seen; but if 

 on the same scale one of 130° be employed, half of the lines 

 will disappear, which proves that the first efiect was due to 

 interference. 



Battledoor Scale of Polyommatus Argiolm (Azure blue). — 

 One of these elegant scales is represented at fig. 3, plate viii., 

 as seen under a magnifying power of 500 diameters ; when 

 badly defined, its surface appears covered with coarse longi- 

 tudinal striae ; but under a good object-glass, the strias are in- 

 terrupted by small rings having a hair-like projection from the 

 centre of each ; the rings are at some little distance apart, and 

 are joined together by minute longitudinal striae ; in the lower 

 part of the scale there is a curved band with its convexity to- 

 wards the point of attachment of the scale, which consists en- 

 tirely of minute black dots of pigment ; the striae between this 

 band, and what may be termed the quill of the feather, are not 

 interrupted by rings, but consist of continuous lines, having 

 black dots upon them. A good defining power should show 

 the dots in the rings and the connecting striae between each 

 very distinctly. 



made out by second-rate instruments, hence some caution is necessary 

 that proper scales be selected for examination, the best of all being those 

 of the kind shown by fig. 5. 



