PROCEEDINGS OF THE SOCIETY. 989 



Mr. Teesdale referred to tlie instrument designed by Professor 

 Suringar, of Holland, for testing the accuracy of micrometers, which 

 was exhibited at the loan collection of scientific instruments at South 

 Kensington. 



Mr. Forrest's paper "On the Anatomy of Leptodora hyalina," was 

 read by Mr. Crisp, the figures in illustration being enlarged upon the 

 blackboard by Mr. Stewart (see p. 825). 



Mr. J. Fullagar's Note on a curious fresh-water organism, which 

 he had discovered, was read by Mr. Crisp, together with a letter from 

 Mr. Saville Kent, who said that as far as he could judge it was closely 

 allied to the marine Freia ampulla of Claparede and Lachmann, the 

 tubes in one specimen having been apparently deserted by the Infusor 

 and occupied by Eotifer, and promising to give a more precise deter- 

 mination on the receipt of living specimens. 



Mr. Stephenson's paper "On a Table of Numerical-Apertures, 

 showing the Equivalent Angles of Aperture of Dry, Water Immer- 

 sion, and Homogeneous Immersion Objectives, &c.," was taken as read 

 (see p. 839). 



Mr. Mayall's paper " On an Immersion Stage Illuminator," was 

 read by Mr. Crisp, and the apparatus which it described exhibited 

 (see p. 837). Another paper, " Aperture Measurements of Immersion 

 Objectives expressed as ' Numerical- Aperture,' " was taken as read 

 (see p. 842). 



Mr. Crisp read various letters and other communications received 

 from provincial and foreign societies in connection with the Ex-officio 

 Fellowship. 



The President announced that the first Scientific Evening of the 

 session would be held on December 3rd, in the Library of King's 

 College. 



The following Objects, Apparatus, &c., were exhibited:— 



Mr. Badcock : — Abnormal forms of Acinetce. 



Mr. Bolton: — Ophri/dium versatile, and Limuias ceratojjlnjlU. 



Mr. Crisp : — (1) Zeiss's travelling Microscope (see p. 955). (2) 

 Improved apparatus for counting blood-corpuscles (see p. 944). 



Mr. Forrest : — Two slides of Leptodora hyalina. 



Mr. Graham : — New compressorium. 



Mr. Mayall, jun. : — Stage immersion illuminator. 



Mr. Ward : — (1) Improved microtome (see p. 957). (2) Sections 

 of wood of Antiaris toxicaria (upas tree of Java) ; double stained. 



