660 PROCEEDINGS OF THE 



from that locality, and is covered with a network of dark, well- 

 defined secondaries, except on the parts occupied by the large 

 primaries. Each of the dark secondaries splits up into three or 

 four parts by a bright cross-bar arrangement. This structure 

 requires a good oil-immersion objective and a very considerable 

 magnification to render it readily discernible. 



A photograph of the above was exhibited, and Mr. E. M. 

 Nelson, F.R.M.S., confirmed the presence of this structure from 

 a specimen in his cabinet. Mr. Merlin also exhibited two other 

 photographs of a diatom. Mr. Nelson had written him that he 

 had discovered that Coscinodiscus simbirsJiii, which, with ordinary 

 transmitted light, resembles Coscinodiscus asteromphalus , when 

 examined with a dark ground and a rather small stop looks like 

 Actinoptychus splendens. This led him to search for the diatom 

 specified, and although this could not be found, he found one 

 which, with a dark-ground illumination, revealed a beautiful 

 radiating structure, somewhat resembling a Heliopelta, which 

 was not observable by transmitted light. On the photographs 

 of this specimen being examined it was identified by Mr. Mor- 

 land as Janischia antiqua, Grunow. Mr. Merlin further pointed 

 out that, although diatom-dotting has influenced the develop- 

 ment of the microscope towards perfection more than anything 

 else, he is unable to find out particulars of its introduction. Mr. 

 Nelson sent an extract from Messrs. Sollitt and Harrison's 

 paper, read before the British Association at Hull in 1853 : 

 " We in Hull first discovered the delicate markings on their 

 silicious coverings, and pointed them out to others as the proper 

 tests for lenses. The first of the Diatomaceae on which the 

 lines were seen was the Navicula hippocampus of Ehrenberg 

 this was early in 1841, when specimens were sent to the 

 Microscopical Society of London also to Mr. Smith, Mr. 

 Ross, Messrs. Powell & Lealand, M. Nachet in Paris, and Pro- 

 fessor Baile} 7 in America, all of whom at once saw the excellency 

 of these objects as tests for the microscope." 



At the 508th Ordinary Meeting of the Club, held on Tuesday, 

 May 25th, the Vice-President, Mr. D. J. Scourfield, F.Z.S., 

 F.R.M.S., in the chair, the minutes of the meeting held on 

 April 27th were read and confirmed. 



