132 



The scale is then slid along the rod until a div^ision of the stac^e 

 micrometer corresponds (for convenience) with an even number of 

 divisions on the scale. This is noted, and the object to be 

 measured is placed on the microscope stage. Its real size is at 

 once deducible from the number of divisions, of which the value 

 is known, that its image is observed to occupy on the ivory scale. 

 The rod carrying the scale being divided, it is only once necessary 

 to ascertain for each combination of objective, eye-piece and 

 varying tube-length employed, the position on the rod that the 

 scale is to occupy, to hav^e a most convenient and efficient form of 

 measuring instrument. 



Mr. Stokes also referred to the convenient method of using 

 squared paper for the purpose of finding intermediate values of 

 magnification with varying tube-lengths, when only two or 

 more values, with the same combination of objective and eye- 

 piece, but with differing tube-length, are known. Examples were 

 given. 



Mr. C. Lees Curties, for Mr. C. Baker, exhibited a number 

 of preparations of Crustacea injurious to wooden piers and 

 piles. Four of the preparations were of amphipods and five 

 of isopods, of which latter were included specimens of the very 

 rai'e Leptochelia sairgnii and Arcturus sp. There was also shown 

 ,a specimen of the exceedingly rare Sphaerosyllis hystrix, carrying 

 embryos. Very little is known of the development of this form. 

 It is illustrated in Mcintosh's Worms, the last volume of the 

 Publications ('tto) of the Ray Society. 



The thanks of the meeting were accorded to Mr. Lees Curties 

 for his interesting exhibit. 



Mr. A. E. Hilton exhibited a preparation of the Mycetozoon 

 Spumaria alba (Aethalium) x 20, and Mr. A. Earland showed 

 living Diffliigia sp. 



At the meeting of the Club held on June 28th, 1910, at the 

 Dore Gallery, New Bond Street, Mr. C. F. Rousselet, F.R.M.S., 

 Vice-President, in the chair, the minutes of the meeting held on 

 March 24th were read and confirmed. 



Mr. Alfred E. Charlton was balloted for and duly elected a 

 member of the Club. 



The list of donations to the club was read and the thanks of 

 the members were voted to the donors. 



