256 Transactions of the Royal Microscopical Society. 
Note by John Anthony, M.D. 
Having read Dr. Woodward’s paper on the gnat and mosquito 
scales, and looked carefully at the set of photographs in illustration, 
which that gentleman has had the kind courtesy to forward to me, 
I can come to no other conclusion but that what I have hitherto 
regarded as real bead markings on the membrane in the intercostal 
spaces on the scales from the body of the gnat are really and truly 
spurious images, or, in the words of Dr. Woodward, “ diffraction 
appearances.” 
Some two years ago, in the examination of a large number 
of gnat scales, principally with the fine |th and T Vth objectives of 
Messrs. Powell and Lealand, such results were obtained that I 
thought I had found in the scale from the body of the gnat an 
excellent test for the “ definition ” of high-power objectives, inas- 
much as there seemed, with moderately oblique and well-corrected 
light, what appeared to me triple rows of clearly defined beads 
between the beaded longitudinal ribs of the scale ; and, as the same 
appearances of beads were always manifest, and as those beads 
always seemed to come out clearer when viewed with objectives 
of well-known excellence, I trust to be pardoned for believing that 
what I saw were not only real appearances, but that such objects as 
the gnat scales might be of the greatest service to the microscopist 
as tests for the defining qualities of high-power objectives. Under 
such impression I made a careful drawing of the markings on the 
gnat’s scale under the most favourable conditions, and that drawing 
I copied by means of photography; the photograph would have 
been made directly from the scale of the gnat itself, but I had no 
heliostat. These photographic copies of the drawing have gradually 
passed into the hands of one or other of my microscopical friends 
until the specimen forwarded with this paper is the only one left 
to me. However, I have the negative, and if possible impressions 
shall be printed for distribution among the members present at the 
next meeting of the Society.* (PI. CXXXIX.) 
Taking the E, F, and Gr photographs of Dr. Woodward to be 
the most characteristic, inasmuch as they show respectively two, 
three, and four rows of beads as seeming to exist upon the same 
scale under different conditions of illumination, I think one can 
only look upon my drawing as a representation of very clearly seen 
spurious beads. Of course it is not very flattering to one’s amour 
propre to have it shown so convincingly that one has taken the 
shadow for the substance ; but I am assured that I shall have erred 
in good company, inasmuch as the analysis of these diffraction 
images will strike at the root of a vast number of descriptions of 
* Some were sent by Dr. Anthony to the meeting. 
