PROCEEDINGS OF THE SOCIETY. 833 



structure, and the bright points in the rosette patterns as due to the 

 illumination. From his own observations he had found that fine 

 undulating continuous lines traversed the whole upper circuit of the 

 disk, and that beneath these radiated others from centre to periphery. 



Dr. Butcher, in reply, remarked that he had nothing further to add. 

 There would be full scope for discussion on the subject, he thought, 

 later, when the diatom had been studied by other observers under the 

 same conditions as those in which he himself had worked. 



The President said that there appeared to have been some difficulty 

 about Mr. Nelson's description of the objective which he used on this 

 particular object. He would like to suggest that, perhaps, the mistake 

 might have arisen, as in other cases, by the use of the word " series," 

 which the Germans used for a batch of lenses ; thus it was quite likely 

 that the words " new series," meaning a new batch of lenses, might 

 have been misinterpreted as referring to a new formula. No new batch 

 of lenses, however carefully made, and however much of the machine 

 was used in their construction, could ever be exactly of the same 

 quality. Thus, in his possession he had a Zeiss apochromatic stated to 

 have a numerical aperture of 1 ■ 40, which was, however, one of 1 ' 44, 

 as measured, and as the Zeiss firm only engrave a minimum value on 

 their lenses, some such error, in the right direction, might be attributed 

 to Mr. Nelson's lens. The Society was always grateful for any work 

 on diatoms, as this work had, more than any other, led to the perfecting 

 of our Microscope lenses. He was sure that all present were very deeply 

 obliged to Dr. Butcher for his interesting paper, and proposed a cordial 

 vote of thanks to him, which was carried with acclamation. 



In the absence of the authors, Mr. Shillington Scales read a paper 

 by the Rev. Hilderic Friend, on "New British Enchytraeids," and also 

 one by Mr. Walter Bagshaw, on " Instantaneous Exposure in Photo- 

 micrography." 



Mr. Barnard remarked that he thought that the method described 

 was not entirely novel, as magnesium had been used as an illuminant 

 from the early days of photomicrography. In his experience, the crux 

 of the whole operation in instantaneous work of this character lay in 

 having some arrangement for observing the image. There appeared to 

 be no suggestion of such in the method described. The actual appear- 

 ance of the object, therefore, whether in focus at the moment of 

 exposure, or indeed, whether in the field of view at all, was left to 

 chance. Further, the area of the illuminant is very large in flash-light 

 work, and this is a fatal objection to its use for anything but the 

 lowest powers. 



The thanks of the Society were returned to Mr. Friend and to 

 Mr. Bagshaw for their communications. 



The President said that before they separated there was a matter 

 about which he particularly wished to speak. When the Royal Micro- 

 scopical Society was inaugurated many years ago, a book — the " Roll " 

 of the Society — was commenced. This book contained the Charter of 

 the Society, but also contained several double-column pages of very dis- 

 tinguished names of earlier Fellows of the Society, beginning with dames 



