IV CONTENTS. 



PACK 



C. D. Soar, F.L.S., F.R.M.S. Description of Arrhenurus Scour- 

 fieldi and Acercus longitarsus, Two New Species of Water- 

 mites (Plates 12 and 13) 130 



G. T. Harris. The Collection and Preservation of the Hydroida 143 



T. A. O'Donohoe. The Minute Structure of Coscinodiscus 

 asteromphalus and of the Two Species of Pleurosigma, 

 P. angulatum and P. balticum . . . . .155 



Henry Sidebottom. Lagenae of the South-West Pacific Ocean 



(Supplementary Paper). (Plates 15-18) . . .101 



James Murray, F.R.S.E. Gastrotricha (Plate 19) . . 211 



Notes. 



Edward M. Nelson, F.R.M.S. On a New Method of Measuring 



the Magnifying Power of a Microscope . . ,239 



Proceedings, etc. 



Proceedings from March 25th, 1913, to June 24th, 1913 . 245 



Obituary Notice : Rt. Hon. Sir Ford North, F.R.S., F.R.M.S. . 258 



PART No. 74. APRIL 1914. 

 Papers. 



Arthur Dendy, D.Sc, F.R.S. President's Address Organisms 



and Origins ........ 259 



S. C. Akehurst, F.R.M.S. A Changer for Use with Sub-stage 



Condensers (Figs. 1 and 2) . . . . . .277 



S. C. Akehurst, F.R.M.S. A Trap for Free-swimming Or- 

 ganisms (Fig. 3) . . . . . . . . 279 



E. M. Nelson, F.R.M.S. An Improved Form of Cheshire's 



Apertometer (Fig. 4) . . . . . . .281 



F. J. Cheshire, F.R.M.S. Two Simple Apertometers for Dry 



Lenses (Figs. 5 and 6) ..... . 283 



M. A. Ainslie, R.N.. B.A., F.R.A.S. A Variation of Cheshire's 



Apertometer (Figs. 7 and 8) . . . . . 287 



James Burton. On the Disc-like Termination of the Flagellum 



of some Euglenae . . . . . . 29 J 



E. M. Nelson, F.R.M.S. On the Measurement of the Initial 



Magnifying Powers of Objectives (Fig. 9) . . . 295 



S. C. Akehurst, F.R.M.S. Some Observations concerning Sub- 

 stage Illumination (Plates 20-22) . . . .301 

 T. A. O'Donohoe. An Attempt to Resolve and Photograph 



Pinnularia nobilis ....... 309 



N. E. Brown, A.L.S. Some Notes on the Structure of Diatoms 



(Plate 23) 317. 



Notes. 



James Burton. On a Method of Marking a Given Object for 



Future Reference on a Mounted Slide. . . .311 



