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PEOCEEDINGS OF THE SOCIETY. 
Meeting op 15th October, 1890, at 20, Hanover Square, W., 
the President (Dr. C. T. Hudson, LL.D., F.K.S.) in the Chair. 
The Minutes of the meeting of 18th June last were read and 
confirmed, and were signed by the President. 
The List of Donations (exclusive of exchanges and reprints) received 
since the last meeting was submitted, and the thanks of the Society given 
to the donors. 
From 
Jelly, E. 0., A Synonymic Catalogue of the Recent Marine 
Bryozoa, including Fossil Synonyms, xv. and 322 pp. 
(8vo, London, 1889) Miss E. C. Jelly. 
Marktanner-Turneretscher, G., Die Mikrophotographie als 
Hilfsmittel naturwissenschaftlicher Forschung. vii. and 
344 pp., 195 figs, and 2 pis. (8vo, Halle a. S., 1890) . . .. The Author. 
200 slides of Marine Bryozoa Miss E. C. Jelly. 
12 Photomicrographs of Diatoms, &c j Dr '® l pi^ e ^ ter 
Attention was called to a donation of special importance, consisting 
of 200 slides of Marine Bryozoa, from Miss E. C. Jelly, who had 
recently published a catalogue of Bryozoa. 
A work on photomicrography, in German, by Herr G. Marktanner- 
Turneretscher, by whom it was presented to the Society, was referred to 
by Mr. J. Mayall, jun., who said the author had dealt somewhat fully 
with descriptions of the various forms of heliostats, commencing with 
that designed by Meyerstein. This heliostat was, he thought, one of 
the simplest and least expensive in commerce, and he exhibited one and 
explained its construction. The modification required in the construc- 
tion in order to meet Mr. Comber’s suggestion, contained in his paper 
on a new heliostat published in the August number of the Journal, was 
to substitute for the existing mirror — which was simply of glass silvered 
at the back, and consequently gave two reflections — a more perfect 
reflecting surface. Mr. Comber recommended a plane mirror of speculum 
metal ; but as such mirrors were difficult to obtain and costly, and, 
moreover, required great care in handling, Mr. Mayall thought that 
possibly a right-angled prism of white glass might be applied with 
advantage. Such a prism might be freely handled, and the internal 
reflection from the hypothenusal face would be extremely bright and free 
from colour. Another such prism might replace Mr. Comber’s fixed 
speculum mirror for deflecting the light from the heliostat mirror into 
the axis of the Microscope supposed to be horizontal. Probably the 
most efficient way of dealing with the matter practically would be to 
bring it to the notice of the mechanician who supplied Meyerstein’s 
heliostat, which he (Mr. Mayall) would endeavour to do. 
Mr. Mayall also directed attention to the donation of 12 photo- 
micrographs by Dr. Giorgio Eoster, of Florence, some of which appeared 
to him excellent specimens of work produced with Zeiss’s apochromatic 
