200 T. P. SMITH ON BUTTERFLY AND MOTH SCALES. 



rows some distance apart. In the specimen shown to-night the 

 under corrugated membrane, with the cross-bars, has been torn 

 away from a considerable part of the scale, but has left the upper 

 smooth membrane intact. Now this upper smooth membrane, from 

 its thinness, is optically non-existent when mounted in balsam, un- 

 less you can focus on the broken edge ; but its presence is 

 apparent here from some of the villi remaining attached to the 

 under side. Had the whole of the villi remained intact it would 

 have pointed to the probability of their being outside ; but as the 

 most of them are gone they were evidently torn away with the 

 under membrane. There seem to me, then, to be two points 

 settled. First, that all butterfly and moth scales have certain 

 projections or villi, springing from their surfaces ; and that, 

 secondly, these projections are contained between the two mem- 

 branes of the scale. They assume various forms, consisting in 

 some cases of little tufts branching from one root or point ; in 

 others of little rods tapering at one end, which run straight from 

 one membrane to the other ; in others they have a distinct stem 

 with a rounded head ; and in others are simply bosses standing on 

 the ribbings and cross-bars. 



I assume their purpose is to separate one membrane from the 

 other, and the villi are more or less pronounced in character 

 according to the distance the membranes are separated. They 

 differ, even in the same scale, and are always largest in the quill, 

 which they keep expanded by interlacing in all directions. 

 Various also, is the manner in which they are distributed in the 

 scales of different species, and I don't think diatoms themselves can 

 show more distinct forms. 



Dr. Pigott, in his papers on this subject, has spoken many times 

 of isolated beading in the scales, and his last paper to-day almost 

 deals exclusively with this point. My own opinion, however, after 

 a careful examination of many scales, is that there is no isolated 

 beading, but that in all cases they spring from the ribs or the 

 cross-bars. 



