196 



to more accurate methods employing a stage micrometer and a 

 camera lucida. The essential points to be observed when using 

 any of the methods demonstrated were clearly pointed out. 

 Wright's Eikonometer — a very convenient piece of apparatus 

 designed to the same end — was also exhibited. The use of the 

 eyepiece micrometer in measuring the size of objects when the 

 magnifying power of the particular combination of objective, eye- 

 piece, and tube-length employed is known, also received attention. 

 The last exhibit was an improved form of the Cheshire Apertometer. 

 This consists of a circular disc of glass with a mark on the upper 

 surface, to which the object-glass to be tested is focussed. The 

 lower surface of the disc is ruled with a series of concentric rings, 

 each of which is placed so as to correspond to "1 N.A. The method 

 of use was to place the Apertometer on the stage, and focus the 

 cross-lines ruled on the upper surface. The eyepiece is then re- 

 moved, and the number of rings visible in the back lens of the 

 object-glass is counted. This number equals the N.A. of the 

 objective examined. For high powers a special eyepiece, which 

 focusses to the back focal plane of the objective, is inserted in 

 place of the usual eyepiece. 



The Hon. Secretary read a list of recent presentations, the 

 chief of which were forty preparations, chiefly of scale insects and 

 mites, from the collection of the late Rev. J. R. Ward, of Natal, 

 presented to the cabinet by Mr. R. T. Lewis, F.R.M.S. ; twenty- 

 three preparations of fresh-water Rhizopoda, presented by Dr. 

 E. Penard. These, with a previous donation of twenty-two, make 

 a valuable type collection, which will be of very great use for 

 identifying specimens to any members taking up the systematic 

 study of this group. 



Mr. D. J. Scourfield, F.Z.S., F.R.M.S., said that it had been 

 thought that a few words about fresh-water rhizopods would be 

 a suitable introduction to the paper by Dr. Penard which was 

 to follow. He said he was glad of the opportunity of directing" 

 attention to a group of organisms which has been very much 

 neglected — not neglected so much, it is true, as the Tardigrades, 

 about which a paper was read at the last meeting of the Club, 

 but certainly not receiving from our microscopists the attention 

 deserved. This seems rather strange, as these little animals are 

 very plentiful, and are externally very beautiful, often with 

 delicately formed and perforated tests. The problems in connec- 



