304 
PROCEEDINaS OF SOCIETIES. 
tion to the study of diatoms, though quite enough to enable him to 
see the importance of Dr. Woodward's observations. 
Mr. J. Mayall, jun., said : Dr. Woodward has made an exhaustive 
examination of one of the finest known test-diatoms by means of pho- 
tography, and he has supplemented this by critical observations on 
the true definition of the diatom, which, coming from so practised an 
observer, must together go far to settle the question — so far as it can be 
settled with the optical means at present available. I am particularly 
interested by what appears to me an original observation of Dr. Wood- 
ward's, — I refer to his suggestion for readily distinguishing diffraction 
lines from real lines existing in the object. He observes the diffrac- 
tion lines have this peculiarity, that they appear to increase or 
decrease in number as we approach to or recede from the focus of the 
real lines; whereas really existing lines in an object do not appear to 
vary in number when viewed slightly within or without the true 
focus. This is, I think, a highly important distinction, and if care- 
fully mastered by microscopists will lead to greater certainty of inter- 
pretation. Dr. Woodward also calls our attention to the fact that 
photography gives as much apparent reality to the images of diffrac- 
tion lines as to those of lines actually existing in the object : this is 
manifest in the photographs of Frustulia Saxonica which he has for- 
warded to us in illustration of his remarks. With regard to the 
distinction attempted to be drawn by Mr. Hickie between the de- 
finition of the diatom Frustulia Saxonica and what he alleges to be 
another diatom going by the name of Navicula crassinervis, I know 
the diatom well, and have always regarded the two names as applying 
to the same object. MoUer uses either or both names in describing 
it, and I venture to think his opinion is far more valuable than 
Mr. Hickie's. 
Mr. Slack said he did not know the object, but he thought that the 
fact mentioned by Dr. Schumann that there were two marginal edges 
was quite sufScient to account for the diffraction lines. 
The President announced that arrangements had been made for 
carrying out the proposal to hold a scientific evening on the 24th 
instant ; also, that at the next ordinary meeting a paper would be read 
by Professor T. Rupert Jones, entitled, " Remarks on the Forami- 
nifera, with special reference to their Variability of Form, illustrated 
by the Cristellarians. 
Donations to the Library from October 6, 1875 : 
From 
Nature. Weekly , . , The Uditor. 
Athenaeum. Weekly Ditto. 
Society of Arts Journal Society. 
Transactions of the Linnean Society. Five parts Society. 
Journal of the Linnean Society. No. 8 Ditto. 
Transactions of the Royal Irish Academy. Fourteen parts Academy. 
Proceedings of the Eoyal Irish Academy. Five parts . . , . Ditto. 
Canadian Journal. No. 83. 
Bulletin de la Societe Royale de Botanique de Belgique. 
Five parts Society. 
Ten Micro-photographs of Sections of Teeth, illustrative of 
Dental Surgery, by Dr. W. H. Rollins, of Boston, U.S.A., 
produced by Tolles' lenses Chas. Stodder, Esq.. 
