Tur Microscope. 119 
objective under a large axial cone; in the former case only 
crossed striae, or checks could be made out, but in the latter the 
minute grating should be clearly seen. 
This minute grating I have never seen so sharply defined as 
with this new objective when illuminated by Powell’s achromatic 
condensor with full aperture. It shows the following very del- 
icate objects most distinctly : fracture through the delicate per- 
forated membrane inside the large areolations in /sthmia nervosa, 
and the fracture through the still more minute perforations , 
inside the hexagonal structure of Triceratium favus. This last 
object may be termed the highest test to which the ‘ microscopy ’ 
of the present day can be subjected. Thoseinterested in oblique 
light will be glad to hear that the striae on A. pellucida come out 
sharper than I have ever seen them before. The valve is re- 
solved from tip to tip, showing that the lens is flat in its field. 
To sum up, this lens is decidedly the most brilliant objective I 
have everseen. . . . After mentioning the above tests, it is 
almost unnecessary to say that bacteria, stained and mounted 
in balsam, are most clearly defined.” 
Mr. Nelson subsequently wrote us that he had discovered a 
very minute perforation on the interior lining membrane of 
Eupodiscus Argus. This diatom consists of two separate mem- 
branes. The outer one has a brown tint with transmitted light, 
but appears white and sparkling, not unlike loaf sugar, with re- 
flected light. This outer membrane has large and for the most 
part oval areolations all over it, the interspaces being granulated. 
The inner membrane, which is very transparent, has rows of 
comparatively large white dots radiating from the centre of the 
diatom. The whole of this inner membrane between these 
white dots is covered with very minute perforations. These 
perforations are often arranged in circular rows round the white 
dots, and are, in reality, “ tertiary ” markings. 
There is, so far as he is aware, no record of a “tertiary ” 
marking on a diatom having been observed before.-—Jowrnal 
Royal Mic. Soc. 
—_—_\_———torn_—_ 
Mounting Toncurs of Fries.—Flies may be made to pro- 
trude their tongues by dropping them into spirit of wine. They 
die with the tongue well extended, and the death is probably as 
humane as any other. 
