Markings of Frustulia Saxonica, By Br. J. J. Woodward. 279 
Frustulia Saxonica." Mr. Hickie asserts that there is a difference, 
but does not make clear in what the difference consists. I should 
be happy to learn further from him on this head, if he has any- 
thing to teach. If, on examining my photographs, he thinks they 
represent something different from his slides of Frustulia Saxonicaj 
I should be glad to receive one of these from him to study. I have 
the less hesitation in asking this favour, as he tells us his collection 
of these slides is a very extensive one. 
I conclude these remarks with the hope that Mr. Hickie will 
find them as courteous as I acknowledge his own to be. 
List of Photographic Prints accompanying Dr. Woodward^s " Note on the Markings of 
Frustulia Saxonica.'^ 
A. — Print from the negative used to illustrate Dr. Woodward's paper in the 
' Lens,' X 1750 diam. 
B. — Frustule photographed for the present paper to show the transverse striae, 
X 1830 diameters. 
C— Same frustule, same power, showing both transverse and longitudinal lines. 
D. — Same frustule, same power, showing the longitudinal lines of Dippel. 
E. — Same frustule, same power, showing longitudinal lines similar to those 
described by Mr. Hickie. 
F. — Print from a negative made in 1872, showing the transverse striae on one 
frustule, and longitudinal lines on parts of others. 
EXPLANATION OF PLATES CXXIV. AND CXXV. 
These Plates contain figures the same size as those in the several admirable 
photographs which Dr. Woodward transmitted to us. The various figures are 
given in the same order — A, B, 0, &c. — as those above. Whereas, however, in 
the photographs more than one diatom is occasionally introduced, in the Plate 
but a single frustule is represented. 
[The following remarks are contained in the * Lens,' October, 
1872.] 
Note on the Frustulia Saxonica as a Test of High-Power 
Definition. 
The genus Frustulia (Agardh) includes several species of diatoms 
which possess bacillar or navicular frustules, " immersed in an 
amorphous gelatinous substance." * The species are divided by 
Pritchard into two groups, the first with " evident striae," while 
in the second the striae are " wanting or very indistinct," In the 
second group Pritchard places the species Saxonica (Eabenhorst), so 
called from having first been noticed in Saxony, where it " forms 
dirty, olive-brown, tremulous jelly-like masses in little cavities of 
damp rocks." The ' Micrographic Dictionary ' (second edition) 
* ' A History of Infusoria.' By Andrew Pritchard. 4th edit., London, 1861, 
p. 924. 
