QUEKETT MICKOSCOPICAL CLUB. 191 



The list of Donations to the Library included four books 

 from the late Librarian, Mr. Alpheus Smith — for which the 

 ■cordial thanks of the Club were returned. 



Mr. Chapman Jones read a short paper on " The Secondaries 

 or Dotted Structure in the Pinnulariae." This explained and 

 described a series of photographs which he exhibited. He said 

 that about forty-five years ago Mr. H. J. Slack contributed 

 a, note to the Royal Microscopical Society, in which he remarks 

 that at one time it was supposed that the Pinnulariae were dis- 

 tinguished from allied forms by solid costae replacing beaded 

 "bands, but subsequently this distinction was not considered 

 valid. That an examination of the Pinnulariae on Moller's 

 type-slide led to the belief that instead of broad, irresolvable 

 ribs, a truer view of the costae showed fine lines of beads spring- 

 ing from the median band, with a furrow between them, and in 

 that farrow another line of beads at a lower level. 



In a discussion which followed, Mr. O'Donohoe said he was 

 glad Mr. Chapman Jones had brought the subject before them. 

 When he had done so it was considered by a few members that 

 the structure had no real existence, but Mr. Chapman Jones 

 had quite confirmed his ideas on the matter. 



There were seven photos exhibited, taken with a 2-mm. Holos 

 objective, N.A. 1*36, x 8 compensating eyepiece, and a Holos 

 immersion condenser. In some the effects of a solid central 

 cone of light were shown, while others were taken with oblique 

 light and a green screen. The magnification was from x 1,200 

 to X 1,300. In all of them the dots were visible and bore out 

 the author's contention that they occurred on a membrane, 

 which, under normal conditions, would form part of the struc- 

 ture of the diatom-valve as usually seen. The chairman ex- 

 pressed the gratitude of the meeting to the lecturer for his 

 interesting exhibit and the paper explaining it. 



The Hon. Secretary then read a paper by Mr. A. A. C. Eliot 

 Merlin, F.R.M.S., on " Nitzschia singalensis as a Test Object 

 for the Highest Powers." Mr. Merlin had received from Mr. 

 E. M. Nelson a styrax mount of N. singalensis from Amherst 

 in Burma. Its minute structure is similar to that of other 

 varieties of the genus, but is extremely fine. The transverse 

 striae had been seen by Mr. Nelson, but most other micro- 

 scopists had failed to make them out. Mr. Merlin thought that 



