PROCEEDINGS OF THE SOCIETY. 141 



subscriptions, so that Fellows elected in any montli after February 

 would only be called upon to pay a proportionate part of the sub- 

 scription. 



Mr. Crisp exhibited Beck's Miner's Binocular Microscope, intended 

 for rough use in the field, and a photograph by Mr. Jennings of • 001 

 grains of arsenic x 400. 



Mr. Beck exhibited and described a new achromatic condenser 

 for dry and immersion objectives, with five different front lenses set 

 in a drum capable of being rotated consecutively over the back 

 combination, and giving apertures from 7° in air to 110° in glass 

 (1-25 N.A.). Mr. Beck stated that the mode of setting the front 

 lenses avoided the inconvenience of having the immersion medium 

 drawn away by capillary attraction, as would be the case if the 

 lenses were mounted on a flat surface, as in previous forms. 



Mr. Stewart exhibited and described a specimen of Gregarinidse, 

 from the vesiculse seminales of the earth-worm, and explained their 

 mode of growth and development, calling attention to the spines 

 frequently observed upon them, and which he inclined to believe were 

 bond fide cuticular appendages. 



Mr. J. W. Stephenson read a paper "On Mounting Objects in 

 Phosphorus, and in a solution of biniodide of mercury and iodide 

 of potassium," in which he explained in detail the methods which 

 he had found the most successful for the purpose. 



Mr. Stewart thought that the biniodide would prove of very 

 great value as a mounting medium, on account of another of its 

 qualities not alluded to in the paper, namely, its chemical properties 

 as an antiseptic. He believed he was correct in saying that it 

 possessed the valuable power of preserving the colours of many 

 delicate vegetable tissues, and that chlorophyll was not changed by it ; 

 blues would be found to fade a little, but red was kept well, and he 

 thought that the fluid promised to be of great value in mounting such 

 organisms as desmids, the beauty of which was so greatly increased 

 by seeing them in their natural green colour. 



The President said it occurred to him that these fluids might 

 be also of great use in enabling any one to see other difiicult objects, 

 such, for instance, as coccoliths ; they were very difficult to see in 

 the ordinary way, and he would suggest to Mr. Stephenson to try 

 whether they might not be made out more easily by means of such 

 media as he had described. 



Mr. Crisp read a paper " On the conditions for Utilizing the Full 

 Aperture of Wide-angled Immersion Objectives." 



