CORRESPONDENCE. 
33 
slide of Frustulia Saxonica. This time, instead of bright sunlight, his 
means of illumination were about as bad as bad could be — in fact, 
nothing but his wife’s drawing-room lamp, with a ground-glass top.* 
Nevertheless he succeeded in showing me with my newly purchased 
objective the longitudinal lines as plainly and visibly as any of us are 
ever likely to see our own faces in our looking-glasses. 
Again, in the summer of 1873, when a resident of Dresden, I 
had a visit from Dr. L. Rabenhorst, the well-known author of the 
‘ Siisswasser-Diatomaceen,’ and showed him, at his own request, a 
variety of test-diatoms, such as Navicula crassinervis, Surirella gemma, 
&c., &c., and amongst these one special slide of Frustulia Saxonica, 
which exhibited both lines so clearly and beautifully as to draw from 
him the usual German exclamation of delight and admiration, 
“ Wunderschbn ! ” With Navicula crassinervis he was less satisfied. 
Now, bearing in mind that Dr. Rabenhorst is both the discoverer 
and namer of the diatom in question, I will put it to Dr. Woodward, 
even supposing that Herr Seibert could twice impose upon me for 
Frustulia Saxonica something that was not, whether I could have any 
chance of imposing upon Dr. Rabenhorst after the like manner, or 
upon Herr Alex. Lindig, late Optician to the Court of Saxony, to 
whom I showed it three nights later, who may be credited with the 
ability to recognize the markings of a well-known Saxon diatom when 
he saw them on a slide bearing his own label. 
On turning to my own MS. note-book on test-diatoms, no portion 
of which was written later than the year 1872, I find the longitudinal 
lines of Frustulia Saxonica there described as “ slightly wavy, but 
considerably less wavy and less apparent than in Bhomboides.” The 
plain truth is, I never knew there was any special difficulty about 
these longitudinal lines till I saw it so stated in the (supposed) extract 
from Dr. Woodward’s paper. I will add further, that on the evening 
of the 14th of this month, when it first occurred to me to write on 
this subject, I put upon the stage of the microscope the same slide I 
had shown to Dr. Rabenhorst and Herr Lindig ; and it so happened 
that the very first shell that came in front of the objective exhibited 
precisely the longitudinal lines, and as plainly as I could ever wish to 
see them. Of course I used no condenser. I have always regarded 
that article, when employed on high-power delicate tests, as a mere 
optician’s booby-trap. Its only use there is to disguise the optician’s 
faulty workmanship and to make a bad glass pass muster for a good 
one. 
The reader would do well to see what Dr. Schumann f has to say 
on this point, when about to attack that intricate customer Navicula 
lata. Advanced microscopy under such circumstances is open to the 
gravest suspicions. 
I had also no difficulty in bringing into view those wide-spaced, 
* I intend to forward a copy of this number to Herr Seibert, at his present 
address, so that my statements may come before him for correction, if I have said 
the thing that is not. I am sure he will be not a little surprised to learn that 
Frustulia Saxonica has no visible longitudinal lines. 
t ‘ Die Diatomeen der hohen Tatra,’ p. 73. 
D 2 
