93 



NAVICULA RHOMBOIDES AND ALLIED FORMS. 



By Edward M. Nelson, F.R.M.S. 



{Read June 2StJi, 1910.) 



The reopening of this old story, now dormant for many years, is 

 due to the receipt from Mr. Chaffey of some slides of a gathering 

 of N'. rhomhoides. This gathering proved to be practically identi- 

 cal with that in two old slides labelled "Amician Test." With 

 regard to the question, " What was the Amician Test ? " one can- 

 not do better than study Mr. Karop's excellent paper* on that 

 subject. At the same time the following quotations may be 

 of interest. The first, from an anonymous author, appears as 

 early as 1855: "... also the very delicate markings of the 

 Amician test, Grammatophora subtilissima, and Navicida rhotn- 

 boides. ..." A few paragraphs on we find ". . . A^ rhom- 

 hoides, the Amician test, and Grani'matophora are made . . . " 

 Another comes from America in the game year : " . . . we 

 did not try in this way either the Amici test or the Providence 

 Graminatojyhora. ..." 



The first paragraph seems to show that the Amician test is 

 not the Navicida rhomhoides, the second that it is not a 

 Grammatojyhoyxi, and the third that it is not a Pi-ovidence 

 Grmnmiatophora whatever that may be. 



It is not at all improbable that the Amician Test coming over 

 from the Continent to the Exhibition of 1851 was adopted by 

 Mr. C. M. Topping, who some twelv^e years previously had 

 started business as a professional microscopic-object mounter. 

 There, are two slides in my cabinet labelled "Amician Test." 

 They are dry-mounted spread slides of N, rhomhoides, imperfectly 

 cleaned. One, the older, is mounted between two covers attached 

 by ornamental paper to a mahogany slip with a hole in it ; the 

 other, which was the late Mi-. Hugh Powell's own slide (kindly 

 given to me by Mr. Thos. Powell), is mounted on a glass slip also 

 covered with ornamental paper, having Topping's name on it. 

 The words " Amician Test" are in the same handwriting on both, 



Journ. Q.M.C., ser. 2, vol. 6, p. 79 (1895). 



