325 
was largely talked of by the Fellows of the Society. Dr. Wallich 
asserted that he had found deposits in gutters, and in the outlet 
of the metropolitan main sewer at Crossness, having the charac- 
teristics of Bathybius. 1 The President said that Dr. Beale’s paper 
reminded him of a remark made by Dr. Milner, when asked if he 
could refute Bishop Berkeley’s theory of matter. He replied, “ I 
cannot answer it. It contradicts common sense, and there must 
be great nonsense somewhere He could not say where, how- 
ever. 
May 12 th, 1869. 
The President in the chair. 
Mr. George Busk sent in his resignation as a Fellow of the 
Society, and was elected an Honorary Fellow on the motion of the 
President. 
Mr. B. T. Lowne read a paper on “ The Rectal Papillae of the 
Blow-fly,” and Mr. Suffolk made observations on the proboscis 
of the same insect, and exhibited drawings of it. 
The President described an addition to his kettle-drum con- 
denser, consisting of a third lens. 
June 9 th, 1869. 
The President (Rev. J. B. Reade) in the chair. 
The President described a most valuable new form of illumi- 
nation, which he declared had rendered the microscope a new 
instrument to him. He had by its means been able definitely to 
settle the structural cause of the markings of the diatom valve, 
which he could now demonstrate most clearly, even with a f, as 
spherical nodules arranged in lines. A young friend of his, 
looking at a specimen with this new method of illumination, had 
exclaimed, “ It is just like a dish of marbles.” The illumination 
which was so successful was obtained by means of a prism whose 
section is an equilateral triangle ; by its use parallel direct rays 
are thrown, which avoids the unnatural and deceptive complica- 
tions obtained by the use of converging rays. 
Mr. Wenham remarked that he had shown, by observing the 
form of splinters of fractured diatom valves, that the markings 
on the surface were really due to hemispherical projections. A 
paper by him on this subject was published some years since in 
the ‘ Quarterly Journal of Microscopical Science.’ 
Mr. Eulenstein, the author of the ‘ Series of Diatoms,’ remarked 
that he had, by the most careful study of very many species, come 
to the conclusion that there were two forms of marking in 
diatoms — first, by the framework, consisting of ridges and eleva- 
tions characteristic of genera ; and secondly, by the universal 
1 Has Dr. Wallich ever compared the two appearances, or on what 
ground does he veuture this statement? — E. R. L. 
