180 T. P. SMITH ON THE FINER STRUCTURE OP BUTTERFLY SCALES. 



diameters, and on another plate a part of the same scale magnified 

 1,900 diameters, and drawn from that to a further scale of 4,400 

 to 1. I don't know a better object than the more magnified draw- 

 ing, with which to measure the progress that has been made since 

 that date, with even dry objectives. The drawing shows the 

 structure as shown by Ross' T y objective, considered at that time 

 and for a long time after a king of glasses, but does not show the 

 villi, although " an irregular net-like covering " was apparent to 

 the observer, which he set down as pigment cells. To-night I show 

 the same object under a dry £", just made for me by Swift and Son, 

 and of which the new optical glass forms a component part. For 

 the purpose of comparison with the drawing I have forced up the 

 glass to 1,900 diameters, and the villi are there seen plainly stand- 

 ing up from the crossbars. 



The scales of Ainathusia are mounted dry, but the three other 

 scales which I show are mounted in Canada balsam, and I am 

 indebted for them to Mr Hinton, of Varley Road, Upper Hollo way, 

 without whose aid I could not have shown the structure to-night. 

 By this method all here is plain, while a scale mounted dry will 

 give only the barest indications. 



Allow me here to give my ideas of the structure of the different 

 scales shown under the four microscopes. On the first stand is 

 the Amathusia, which gives the key to all the others, and the 

 structure in this I will try to show you on the blackboard. It is 

 very simple ; longitudinal ribs running from end to end of the 

 scale; cross-ribs at regular intervals, and rising from these two 

 or three beads, some of which seem to stand close on the cross- 

 ribs and some to rise from them with a stalk. On the second stand 

 is a coarse reticulated scale of Morpho mencJaus, and I want to call 

 your attention to the contrast between the coarseness of the main 

 structure and the beautiful minute beads with which it is outlined. 

 On the third stand is a scale of Papilio mcmnon, and nothing- 

 can exceed the beauty of its structure. Instead of a single cross- 

 bar at regular intervals connecting the long ones, they are con- 

 nected by a beautiful interlacing pattern, from which rises 

 numerous minute filaments not more than the 100,000th of an 

 inch in diameter. On the fourth stand is the scale of a moth 

 (Zygoma trigonilla), and here the structure is quite different. I can 

 see no trace of cross- ribbing, but from the inner part of the mem- 

 branes of the scale, I think, a tufted structure springs, which, in 



