62 
Dr. Roberts remarked on the great rarity of cystine 
calculi, many large museums not possessing a single specimen. 
He had in his own collection three specimens, and in the 
museum of the Manchester School of Medicine there were 
portions of two very fine calculi. A certain historical 
interest attached to one of the latter, a piece of which was 
presented by the late Mr. Ransome, to Baron Leibig, during 
one of his visits to Manchester. The analysis of this piece 
led to the rectification of a curious error in the original 
formula for cystine, published by Front and Lassaigne ; these 
eminent chemists had deduced the formula C 6 H 6 N0 8 , but 
the Giessen analysis discovered 20 per cent of sulphur, 
which brought the true formula to C 6 H 6 NS 2 0 4 , the two 
atoms of sulphur having been before erroneously reckoned 
as four atoms of oxygen. 
Mr. J. Sidebotham read the following paper : — “ Notes on 
the pupa and imago of Acherontia atropos.” 
The peculiar cry or squeak of the death’s head moth is 
very well known, and in conjunction with the mark of a 
human skull on its thorax, has no doubt contributed to pro- 
duce the aversion and terror with which the insect is regarded 
by the ignorant and superstitious. 
No other Lepidoptera are known to utter any cry whatever, 
and although many scientific men have engaged in the 
inquiry, it is still uncertain how the moth produces the 
sound. This may seem strange, but as the only observations 
which can be made on the living creature are confined to the 
outer organs, it can only be proved that the sound is not 
produced by the wings, proboscis, palpi, legs or antennae. 
These can be separately or together confined, and still the 
sound is produced, and as to dissection of the insect when 
dead, the only results to be arrived at, are that the sound 
may be produced by certain organs, not that it is. It has 
been by some observers thought this sound is produced by 
