444, Captain J. Mitchell's Remarks, §c. 
that the filament is single. A correct description of the way in 
which the silk is deposited in the cocoon will be found at p. 200 
of Adams’ Essays on the Microscope, published nearly seventy 
years since. 
It is, I believe, commonly supposed that the silk spun by every 
species of silk-producer, that is usually manufactured, is alike in 
form; but that is not the case. All the ordinary silk that I have 
examined is cylindrical, or nearly so; but the common Tussah silk, 
fronr Antherea Paphia, is flat, and I have satisfied myself that each 
filament consists of a large number of very fine fibres held together 
by some substance that makes it very difficult to separate them. 
I have, however, succeeded so far as to justify me in saying that 
the filament is compound, and that the finest fibres I have obtained 
measure about s<45 th of an inch in diameter. 
The filaments spun by Altacus Atlas and Actias Selene also 
appear to be compound, but the structure is not so marked as in 
Antherea, and I have not yet tried to separate their fibres. 
The foregoing remarks on Tussah silk are founded on observa- 
tions made some days since. I have just had time before closing 
this letter to re-examine some that have been in water for many 
days, and I find the filaments are gradually breaking up into their 
component fibres, and 1 hope they will eventually all separate and 
enable me to mount specimens for permanent record. 
I have only to add that, having had occasion to write to Captain 
Hutton, I pointed out the mistake about the filament, and he said 
in reply, that if I had discovered the two filaments were laid side 
by side and not twisted, I ought to make the fact known, as at 
present the idea prevailed amongst Entomologists that the two 
fibres were twisted after issuing from the orifice in the lip. 
