279 Transactions of the Royal Microscopical Society. 
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- 
thins? to teach. If, on examining my photographs, he thinks they 
represent something different from his slides of Frustulia Saxonica, 
I should he 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 
F rustulia Saxonica . 
A.— Print from the negative used to illustrate Dr. Woodward’s paper in the 
j$ . Frus tule 3 photograph ST'for the present paper to show the transverse strife, 
0.— Same frustulefsame power, showing both transverse and longitudinal lines. 
D Same frustule, same power, showing the longitudinal lines of Dippel. 
pj; Same frustule same* power, showing longitudinal lines similar to those 
dpscribod by Mr. Hicki.6. . 
F.— Print from a negative made in 1872, showing the transverse atria 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 wSo^in 
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 m an 
amorphous gelatinous substance.”* The species are divided by 
Shard into two groups, the first with “ evident strip, while 
in the second the striae are “ wanting or very indistinct. In the 
second -roup Pritchard places the species Saxonica (Babenhorst), so 
called from having first been noticed in Saxony, where it “forms 
dirty, olive-brown, tremulous jelly-like masses m little cavities of 
damp rocks.” The ‘ Micrographic Dictionary (second edition) 
* ‘ A History of Infusoria.’ By Andrew Pritchard. 4th edit., London, 1861, 
p. 924. 
