PROCEEDINGS OF THE SOCIETY. 801 



Mr. Rousselet read descriptions of (1) some slides which had been 

 sent to the Society by Mr. Gooding - ; and of (2) three old Microscopes 

 presented as donations to the Society. 



The President expressed the thanks of the Society for the valuable 

 gifts just described by Mr. Rousselet. He would like especially to call 

 attention to the slides sent from Australia by Mr. Allan, who deserved 

 every encouragement on the part of the Society. The slides of Trocho- 

 dota dunedinensis were of great interest, as Professors Koehler and Vauey, 

 two of the leading authorities on Holothurians, had admitted. The 

 Society should thank and encourage a worker whose material was of 

 much interest and beautifully prepared. 



Dr. Hebb read a description of Grayson's Rulings, sent for exhibition 

 by Mr. Merlin. 



Three prints of Mr. Grayson's rulings were exhibited ; these showed 

 the 100,000, 110,000, and 120,000 rulings of his 12-band plate. The 

 special interest in these photographs is that previously nothing over 

 112,595 lines to the inch has ever been exhibited. The prints were 

 accompanied by encomia from Mr. E. M. Nelson and Mr. A. A. C. E. 

 Merlin. 



The thanks of the Society were accorded to Mr. Merlin for his exhibit. 



Dr. Butcher, describing a series of exhibits of photomicrographs of 

 diatoms, said : — " Certain difficulties that I have met with in the course 

 of a study of the various theories advanced in support of the generally 

 accepted conception of what constitutes the microscopic image both in 

 regard to form and colour, led me to attempt to determine for myself 

 some of the physical elements that were possibiy at the root of my 

 mental unrest and incertitude. To this end, amongst objects selected 

 for examination, the group of diatoms as used for test objects naturally 

 presented itself for investigation. But soon, in order to divest myself 

 of prejudices which might have been acquired during years of work, I 

 broke away from the beaten track, worn by the authors and the scientific 

 opticians, and selected other forms — already described, it is true, but 

 usually only from the point of view of classification or life-history. Two, 

 however — Coscinodiscus asteromphalus and Navicula Smithii — have been 

 studied on structural or optical grounds by Mr. E. M. Nelson and 

 Dr. Spitta respectively. As I have been unaware of their labours until 

 some three months ago, the microscopic photographs I present may be 

 taken as an independent confirmation or refutation of the description of 

 their physical characters put forward by the two observers named. I 

 therefore only place them in this preliminary note for that purpose. 



" Coscinodiscus asteromphalus. The specimens of this diatom were 

 obtained from Mr. William Firth, of Belfast, and I here acknowledge to 

 the full that any success I have obtained in the clearness of my results 

 is greatly due to his superb skill as a mounter. The appearances 

 pourtrayed came up with comfort and ease in comparison with the diffi- 

 culties presented by many of my other specimens from other sources. To 

 contirm the results I "have also worked at C. ompMlanthus under 

 exactly similar photographic conditions, and with very similar results. 



