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NOTES AND CORRESPONDENCE. 
Resolution of Nobert’s Lines. — We have to acknowledge the 
receipt from the United States Army Medical Department of 
a further series of most beautiful photographs of Nobert’s 
lines, in which the nineteenth hand has been resolved 
satisfactorily. We shall be glad to make these useful in 
any way to our correspondents who are interested in the 
subject. 
New Test-object. — I beg to describe to microscopists a new- 
test that I have discovered by accident. In the locality of 
Dakar Bango, a little town near St. Louis, in Senega, may 
be found two sorts of spiders ; one, the Epeira, forms a cocoon 
which can be nearly as easily wound as that of the Bombix 
of the mulberry. The silk, of a beautiful yellow colour, has 
the aspect of ordinary silk, only it is much finer and less 
rough. The other spider, known in its native country under 
the name of “ the long spider,” also forms a cocoon, but, as in 
the first, the silk cannot he wound, for the threads are not 
only bound together one with the other, but they are fused 
at regular distances by means of a viscous matter which 
the spider secretes among its work. This gives the cocoon 
great solidity and much elasticity. This cocoon resembles a 
band of thick wool ; nevertheless, seen under the microscope, 
its threads could never be confounded with those of wool, 
although in the country they are given this name. Here, 
then, are the peculiar characteristics of this last-mentioned 
substance, which is nothing but veritable silk, whatever be 
its apparent nature. It is striated in the direction of its 
thickness, exactly as muscular fibres are. With a small 
power some of the threads only appear striated, and the others 
are plain ; but with a power of 600 diameters striae may be 
seen on half those which appear in the field of the microscope. 
A still higher power is required to define the striae of the 
remaining threads. These are, in fact, the threads of the silk 
of the “ long spider,” which I beg to propose as a new test 
for microscopists, and I have a cocoon at the disposal of those 
wishing for specimens. — Mouchet, Rochefort-sur-Mer. 
Some Remarks on Dr. Donkin’s recent Paper on Diatomaceae. 
— The binocular microscope resembles the stereoscope only 
in one particular, namely, that it is an optical instrument 
to which both eyes are applied. In the stereoscope the 
