794 PROCEEDINGS OF THE SOCIETY. 



they would soon die of starvation, but he understood that the cell was 

 primarily intended for much smaller and lower organisms, such as Bacteria, 

 Rhizopods and flagellate Infusoria, for which purpose it would no doubt 

 answer very well. 



The Chairman thought that if the cell was to be used with an oil- 

 immersion objective, a means of varying the thickness of the film was 

 not of much importance. 



Mr. Rousselet considered it was a matter of great importance to the 

 animal. 



The Chairman said one great advantage of this cell seemed to be 

 that it was quite easy to change from a dry to an oil-immersion objective 

 without disturbing the object, as the water was supplied from below, 

 and contrasted it favourably in this respect with the Dallinger life 

 slide. 



Pi 



5 rofessor J. A. Thomson's paper on " Studeria, a Remarkable New 

 Genus of Alcyonarians," was read by Dr. Hebb, and was illustrated by 

 three diagrams, and a specimen shown under the Microscope. 



Dr. Marshall D. Ewell's paper on " The Present Status of Micro- 

 metry," was read by Mr. J. W. Gordon. 



Mr. A. E. Conrady * regarded the paper as of great importance, but 

 thought that the absolute values of the spaces of a stage-micrometer 

 were of the greatest importance, for if these differed from the nominal 

 values, all measurements of focal length of objective and of magnifying 

 power by the usual methods were vitiated. He thought the Society 

 ought to take steps to obtain a standardised Stage-Micrometer, and 

 suggested that the National Physical Laboratory should be approached, 

 as he had recently seen in the last volume of the "Travaux et Memoires" 

 of the International Bureau at Breteuil that there was at Teddington 

 a standard metre sub-divided into millimetres, all errors of which were 

 determined to a few tenths of a micron. 



Mr. F. Shillington Scales said Dr. Ewell had done them a distinct 

 service in bringing this matter before them. Most workers were aware 

 that there was a considerable variation in the rulings of Micrometers in 

 common use, and were accustomed to take the mean of a series of 

 measurements, but it had taken him by surprise to find there was so 

 much variation as was shown by this paper. It was also new to him 

 that glass micrometers deteriorated so much by age, and this was rather 

 a disturbing matter, since he possessed one of Grayson's rulings in glass 

 which was priced at four guineas, and he would be very sorry to find 



: With reference to the extremely interesting communications of the Chairman 

 re work projected at the Standards office, Mr. Conrady begs leave to suggest that, 

 even if this calibration were carried on so as to include the metre as well as the 

 yard, and if the results shoidd disagree with Michelson's, the result could only 

 affect the relation of the yard to the metre and possibly also the value to be as- 

 signed to wave-lengths of light. The metre has been defined by international 

 agreement as the length of a certain Iridio-Platinum bar at the Bureau Interna- 

 tional, and coidd not possibly be affected by this work at Westminster. 



