PROCEEDINGS OF THE SOCIETY. 389 



calcareous or chitinous cement. This is the only foram that secretes a 

 spicule. 



19. Globigerina huUokles, and its isomorph, Haplophragmium glohi- 

 geriniforme, from Indian Ocean, 1300 fathoms. Isomorphism between 

 an arenaceous and a hyaline species. 



20. Triple Isomorphism. Imperforate or porcellanous type, Cornu- 

 spira ; arenaceous type, Ammodiscus ; perforate or hyaline type, 

 SpirilUna. 



'1\. Foraminifera illustrating the three chief divisions : Imperforate 

 or porcellanous ; arenaceous ; perforate or hyaline. Various localities. 



Dr. Wm. Ettles :^Ophthalmometer and Corneal Microscope. 

 Messrs. W. AVatson and Sons : — Expanding Stop for use with a 

 condenser, for dark ground illumination. 



New Fellow. — Mr. F. R. T. Lucas was balloted for and elected a 

 Fellow of the Society. 



MEETING 



Held on the 15th of May, 1907, at 20 Hanover Square, W., 

 The Right Hon. Lord Avebury, F.R.S., etc., President, in 

 the Chair. 



The Minutes of the Meeting of the 17th of April, 1907, were read 

 and confirmed, and were signed by the President. 



The List of Donations to the Society since the last Meeting 

 (exclusive of exchanges and reprints) was read, and the thanks of the 

 Society were voted to the donors : 



From 



Matthews, J. Merritt.— The Textile Fibres. Their Physical,] 



Microscopical and Chemical Properties (8vo, New York| The PublisJiers. 

 and London, 1907) ) 



A Traviss Expanding Stop for Dark-ground Illumination . . Mr. H. Ausbuttel. 



Professor Alfred W. Porter read a paper by himself and Mr. P. F. 

 Everitt on " Diffraction Rings due to a Circular Aperture," in which he 

 stated that he considered the differences mentioned in Mr. Nelson's 

 paper— read on the 21st of March, 1906, and printed in the Society's 

 Journal for October, 1906— between the theoretical and the observed 

 radius of the first dark diffraction ring, must be due to the method of 

 observation, because the values obtained from a very complete series of 

 observations made for him by Mr. P. F. Everitt under the best con- 

 ditions were in very close agreement with theory. 



Mr. J. W. Gordon said it was a little difficult to follow a paper such^ 



