98 EVENINGS AT THE MICROSCOPE 



this peculiarity, that each rib swells at intervals into 

 rounded dilatations, each of which has a minute black 

 point in its centre. In some of these battledoor scales 

 there is, near the lower part of the expansion, a crescent 

 of minute pigment- grains. 



The silvery gray surface of the front wings of a common 

 moth, known as the Buff -tip (Pygcera bucephala), is com- 

 posed of scales of unusual magnitude, and of a remark- 

 able form, their shape being that of an expanded fan, and 

 being quite distinguishable by the unassisted eye. The 

 ribs are very fine and numerous, and there are diverging 

 lines of pigment- grains running through the scale. 



Those of the Emperor Moth (Saturnia pavonia- minor) 

 are likewise triangular in outline, and are remarkable for 

 being deeply notched at the end; so deeply as to leave 

 projecting points (from two to five) as long as, or even 

 longer than the integral portions of the scale. 



In some species we find scales the tips of which are 

 furnished with a curious sort of fringe. This slide pre- 

 sents several such in the midst of many of a more ordinary 

 shape and appearance. The scales in question are straight, 

 and parallel- sided, rather narrow, with the basal end 

 rounded, and the terminal extremity tapered abruptly to 

 a point; it is on each slope of this point that the fringe 

 is arranged. The surface does not appear to be elevated 

 in ribs, but smooth; while the whole interior, except a 

 crescent around the foot- stalk, is filled with pigment- grains, 

 imparting a mottled appearance. It is remarkable that all 

 the scales of this form have the foot-stalk turned in under 

 the expanse. The example which we are considering is 

 from the white portion of the wing of Pieris Glaucippe, 

 a fine butterfly from China; but a similar structure is found 



