368 On the Diatomacece. [Sess. 



ture of at least "90. I have not succeeded in resolving these 

 lines with a dry object-glass. I have done so with Beck's 

 one-tenth water immersion. Then again there is the Amphi- 

 pleura pellucida, which I have succeeded in resolving only 

 with Zeiss 's one-twelfth homogeneous immersion of l - 30 

 numerical aperture. 



It may he desirable that I should name a few books which 

 would be found useful in the study of the Diatomacece. The 

 principal works in English are — 



Smith (Rev. W.) Synopsis of the British Diatomacese, with Remarks 

 on their Structure, Functions, and Distribution ; and Instructions 

 for collecting and preserving Specimens. 2 vols. With 58 plates. 

 Published in 1853 and 1856. 



Donkin (Arthur A. S., M.D.) The Natural History of the British 

 Diatomacese. Parts 1, 2, 3 (all published). 12 plates. 105 figs, 

 of Navicula. 1871-73. 



O'Meara (Rev. E.) Report on the Irish Diatomacese. Part 1 (all 

 published). With 9 plates. 1876. 



Challenger Expedition — Report on the Diatomacese. Prepared by 

 Count Castracane. 30 plates. 1886. This report deals princi- 

 pally with diatoms found in eastern seas. 



Wolle (Rev. Francis). Diatomaceee of North America. With 112 plates 

 and 2300 figs. 1890. 



Van Heurck (Dr Henri). " Traite des Diatomees." Published in 

 English, 1896. This is a very important work. An improved 

 edition in French, of a limited number of copies, to subscribers, is 

 in the press, and is expected to be read}' by June of this year. 



The same author published in 1880-84 his " Synopsis des Dia- 

 tomees de Belgicpie," consisting 'of an Atlas of 132 plates, the 

 "Texte" of 235 pages, and a " Table Alphabetique " of 120 pages. 

 These are in French. 



Pelleton (Dr J.) Les Diatomees. 2 vols. 465 figs in the text, and 7 

 plates. 1888-89. These are also in French. 



In German there are many works published. I need only 

 mention the following : — 



Kutzing (Dr F. T.) Die kieselschaligen Bacillarien oder Diatomeen, 

 30 plates. 1844. And the celebrated "Atlas der Diatomaceen- 

 Kunde " of Schmidt, commenced in 1874 and still being continued. 



In ' Le Micrographe Preparateur ' for November-December 1897 there 

 is an important announcement of the publication of a " Cata- 

 logue general des Diatomees," by M. Maurice Peragalo, intended 

 to replace the catalogue of Habirshaw. This will be an almost 

 indispensable work to all who wish to engage in the systematic 

 study of the Diatomaceae. 



