123 



and a vote of thanks to Mr. Kew for his communication was 

 unanimously passed. 



Mr. D. J. Scourfield exhibited and described Apstein's form of 

 net for quantitative plankton work in lakes and still waters. 



At the meeting of the Club held on June 17th, 190-4, Dr. E. J. 

 Spitta, V.P.R.A.S., etc., President, in the Chair, the minutes of 

 the meeting held on May 20th were read and confirmed, and the 

 additions to the Library announced. 



Messrs. F. J. W. Plaskitt, L. O. Newton, F. G. Lawrence, 

 J. Laws, A. N. V. Waterhouse, and M. W. Ward were balloted 

 for, and duly elected members of the Club. 



Mr. C. D. Soar read a paper descriptive of two new species of 

 Hydrachnida, specimens of which were exhibited in the room. 



The President delivered an extremely interesting lecture 

 " On a Method of Suiting Screens for the Photomicrography of 

 Stained Bacteria." He commenced by saying that as photo- 

 graphy had become the handmaid to microscopy, anything which 

 assisted the photographer in the better and more truthful 

 rendering of microscopical objects really benefited the micro- 

 scopist. It was on this ground that he ventured to occupy the 

 attention of the Club with the subject in question. He added 

 that he wished it to be distinctly understood that he did not bring 

 before them the use of screens for increasing contrast between 

 coloured objects as anything new, but as the method for ascer- 

 taining scientifically the correct antithetical dye to use, by 

 employing the spectroscope in conjunction with the photographic 

 plate, might not be familiar to some of the photomicrographers 

 present, he deemed the subject worthy of a few minutes' 

 attention. Screens were used in photography for two purposes — 

 to improve definition and to increase contrast. He should deal 

 with the latter only. To make what followed better understood, 

 Dr. Spitta carefully called attention to the difference between the 

 human eye and the photographic plate, in their methods of per- 

 ceiving contrast in coloured objects. The eye recognised the 

 difference by contrasting the coloured objects themselves, whereas 

 the photographic emulsion merely recognised differences in intensity 

 of the light from each. For example, red light was merely the 



