PROCEEDlNCiS OF SOCIETIES. 127 



due to any colouring matter in the scales, as chemical agents, 

 which destroy the coloured scales, have no effect whatever on 

 these metallic ones ; lie also mentioned a curious polarizing effect 

 produced by crossing the metallic scales of Plusia. hractea. 



Mr. Sidebotliam exhibited the metallic scales from Plusia 

 orichalcea, Plusia hractea, Plusia Festucce, Plusia concha, &c., 

 illustrative of his remarks. 



It was ultimately resolved that the discussion should be adjourned 

 sons to enable the proposer of the subject, and other gentlemen not 

 present, to express their views. 



jMr. Sidebotham also exhibited a new finder for high powers. It 

 consists of squares formed by crossing lines, one hundredth of an 

 inch apart, enclosing progressive numbers, executed by photo- 

 graphy. He promised to prepare a number for the use of the 

 members, all to be exactly alike. 



Mr. Joy exhibited a nose-piece, made for him nearly two years 

 ago, consisting of a diaphragm plate, under which are screwed 

 four objectives of different powers ; the centreing is so true, that he 

 can use the three-inch as a finder for the 3th or even ith-inch 

 power. Several members of the section have nose-pieces made 

 upon the same principle. 



February 17 ih, 1862. 



Professor Williamson, F.R.S., President of the Section, 

 in the Chair. 



Soundings were acknowledged from Captain W. B. Hall, of the 

 P. and 0. S. S. "Tagus," taken off Ushant, Coast of France, and from 

 Captain J. R. Husband, ship "Florence Nightingale," taken off the 

 Coasts of Patagonia and Tierra del Fuego. 



Professor Williamson called the attention of the section to the 

 new rotifer {Cephalosiphon limnias), recently discovered by Mr. 

 H. J. Slack, in a pond at Hampstead, and an account of which 

 appeared in No. 1 of the ' Intellectual Observer,' of the present 

 month. Attention was specially directed to the fact that the 

 animal only possesses one of those organs that have been designated 

 •'respiratory tul)es," "calcars," and "tactile organs;" whereas, 

 the Floscularian rotifera, when furnished with them, have two. It 

 remains to be ascertained from a study of the embryo, whether this 

 is the typical condition in the Cephalosiphon, or whether there 

 were primarily two, the missing one having been suppressed during 



