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he was before, that the so-called medullary matter is in reality 
a shrunk membrane similar in appearance to the membrane 
in dried quills. Finding that all known solvents of cotton 
gave the same appearances, Mr. O’Neill tried the action of 
solvents on gun-cotton, and found a further confirmation in 
the action of ether upon it. 
It is well known that there are two modifications of gun- 
cotton, one soluble, the other insoluble in ether; but the 
author finds three varieties — (1.) Soluble in ether, but 
insoluble in ammoniuret of copper ; ( 2 .) Insoluble in ether, 
but soluble or dilutable in ammoniuret of copper ; and, (3.) 
Perfectly unacted upon either by ether or ammoniuret of 
of copper. Operating on the first variety on the stage of the 
microscope with ordinary ether, it is almost instantly dissolved 
with no evidence of structure, until, after a while, careful 
observation shows some remains of spiral vessels. By 
gradually diluting the ether with alcohol, the action is 
slackened until a point is arrived at when exactly the same 
phenomena are produced as by the copper solution. About 
two-thirds ether and one-third alcohol was found to be a 
suitable mixture ; but this will evidently vary with different 
preparations. 
Mr. O’Neill considers the number of turns of one spiral to 
be certainly not greater than from 1100 to 1300 in the inch, 
and generally much less than this, the mean of many 
countings running between 600 and 700 for the contracted 
fibre. 
Mr. A. G. Latham made the following communication : — 
It may be remembered that some few months ago 1 pro- 
posed to this Section as a subject for discussion, “The Causes 
of the Metallic Lustre of the Scales on the Wings of certain 
Moths.” 
I then suggested that the metallic markings, and lustre of 
the scales themselves forming these markings, are consequent 
