ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 519 



condition of a body of fresh-water when it is so permeated with one 

 or more species of microscopic algae as to be visibly affected by their 

 presence. In the two instances observed the phenomenon was due to the 

 presence in large quantity of the alga Oscillatoria ; one of the species 

 was probably 0. agardhii, the other is still unidentified. 



The 466th Ordinary Meeting was held at the Morley Hall, Hanover 

 Square, on May 24, the President in the Chair. The Hon. Sec, Mr. 

 W. B. Stokes, exhibited and described a specimen of Burche's micrometer. 

 Messrs. Baker exhibited a number of preparations of Crustacea injurious 

 to wooden piers and piles. Two of the most interesting were of the 

 Isopods Leptochelia sairgnii and Arcturus (?) sp., both very rare. 



The 467th Ordinary Meeting was held on June 28 at the Dore 

 Gallery, New Bond Street, Mr. C. F. Rousselet, Vice-President, in the 

 chair. Mr. A. C. Banfield described and exhibited a sliding nose-piece 

 for taking stereophotomicrographs. Referring to his method described 

 before the Club on October 26 last,* when, to obtain the stereoscopic 

 effect, the object is moved, he said that with low powers and strongly 

 lighted opaque objects the shadow of the object floated in space and 

 gave an irritating result. In the fitting exhibited a sliding plate is 

 screwed to carry the objective which is laterally displaceable by rack- 

 and-pinion. In practice the device works exceedingly well. Trans- 

 parencies were exhibited showing the advantages of the new method. 

 Mr. D. Bryce gave an account of his new " classification of the Bdelloid 

 Rotifera." It is not possible in the space here available to give an 

 abstract of value. The complete paper will be published in the next 

 (November) issue of the Journal of the Quekett Microscopical Club. 

 Mr. E. M. Nelson, F.R.M.S., communicated a paper on " Navicula 

 rhomboides and allied forms." The first part of the paper referred to 

 the old question as to the identity of the diatom known as the Amici 

 test. The author concludes that Professor Amici had no one particular 

 test, and that the test as known in America differed from that used here. 

 In the second part the author suggests the use of an " Index Number," 

 to be used when describing the minute differences of similar species or 

 varieties. Such an index, it is suggested, may be found by dividing the 

 number of the transverse striae by the length-breadth ratio. Examples 

 were given. Mr. A. Ear land read a paper on " Arctic types of Fora- 

 minifera in the North Sea." The material examined was dredged by 

 the s.s. ' Goldseeker,' employed by the International North Sea Com- 

 mission. The particular and characteristic boreal forms were described, 

 and many were exhibited. Concluding his remarks, the author said 

 that in the area of the North Sea, as far north as Noss Head, there is a 

 survival of the fauna of the old Arctic North Sea before the submergence 

 of the land. Among the Orkneys and Shetlands there are records of 

 warm water types which are probably gradually spreading outwards and 

 downwards. 



* See this Journal, 1910, p. 233. 



