, 
JUNE 30, 1923] 
NATURE 
cevii 

MARINE BIOLOGICAL ASSOCIATION 
OF THE UNITED KINGDOM. 
THE LABORATORY, PLYMOUTH. 
The following animals can always be supplied, either living 
or preserved by the best methods :— 
Sycon; Clava, Obelia, Sertularia; Actinia, Tealia, Caryophyllia, Alcy- 
onium; Pleurobrachia (preserved); Leptoplana; Lineus, Amphiporus, 
Nereis, Aphrodite, Arenicola, Lanice, Terebella; Lepas, Balanus, 
Gammarus, Ligia, Mysis, Nebalia, Carcinus; Patella, Buccinum, Eledone, 
Pectens, Bugula, Crisia, Pedicellina, Holothuria, Asterias, Echinus, 
Salpa (preserved), Scyllium, Raia, &c., &c. 
‘or prices and more detailed lists apply to 
Biological Laboratory, Plymouth. 
SCIENTIFIC APPLIANCES 
DALE & HOLLINS 
Electrical, Magnetic, Optical Materials and A ey Dynamos, 
Motors, Insulated Wires, Batteries, Relays, WIR ESS RADIO 
arts and Fittings, Crystals, Valves, ‘Phones, Condensers, New 
THE DIRECTOR. 

P 
Duros Accumulators, do not wear out, Electric Clocks, many . 
new articles. New List free. 
Lenses, Prisms, Mirrors, and all Artists’ Materials and 
Drawing Instruments. Large stock of good Second-hand 
Electrical and Scientific Instruments. full [illustrated List 
6d. post free. See our showroom and windows, or write us. In centre of 
ndon—Top of Kingsway. 
Lond 
SCIENTIFIC APPLIANCES, 11 & 29 SiciLIAN AvENUE, LonDON, W.C.1. 
Pa eet i ee Sai 
HARRINGTON’S 
PURE AND REAGENT 
CHEMICALS 
FOR LABORATORIES. 
Photographic Chemicals. “Technical Chemicals. 


OBTAINABLE THROUGH ALL DEALERS, 
But Specify ‘* Harrington’s.’’ 

Lists on application to 
HARRINGTON BROS., Ltd., 
Wholesale and Manufacturing Chemists, 
4 & 7 OLIVER’S YARD, CITY ROAD, LONDON. 



RHEINBERG MICROMETERS AND OTHER GRATICULES 
By the Processes of 
GRAINLESS PHOTOGRAPHY 
ane 
FILMLESS PHOTOGRAPHY 
RHEINBERG DIFFERENTIAL COLOUR ILLUMINATION 
Complete set of 12 Colour Discs and Rings, 33s. 6d. 
RHEINBERG & Co., 57-60 Holborn Viaduct, London, E.C.1. 
Stock list of standard articles om application. 





OLD PLATINUM, GOLD, 
Dental Alloy, Scrap, &c., 
Purchased for Cash or Valued. 
SPINK & SON, Ltd., 
17 & 18 PICCADILLY, LONDON, W.1. 
EST. 1772, 
Fine Jewels or Plate also purchased or valued. 







PRISM BINOCULARS 
FOR ALL PURPOSES 

By From 
all £2 
Leading List 
Makers free 
CLARKSON’S 
(The Original Firm) 
338 HIGH HOLBORN, LONDON, W.C.1. 
Opposite Gray's Inn Road. Telephone: Holborn 2149. 



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