280 Transactions of the Boyal Microscopical Society. 
gives a brief description of this species, but does not mention the 
striae. 
The first description of the striae with which I am acquainted 
was given by Professor Eeinicke,* who saw fine transverse Hnes, 
but found no objective capable of bringing them out clearly enough 
to count them. (He used immersion objectives of Hartnack.) 
The markings on the Frustulia Saxonica are described and 
figured by Dippel,t whose description is as follows : " The Frus- 
tulia Saxonica possesses longitudinal and transverse striae, of 
which the first are tolerably far apart (from eighteen to twenty to 
the hundredth of a millimeter), the latter, on the contrary, some- 
what closer than those of Grammatophora suhtilissima (from 
thirty-four to thirty-five to the hundredth of a millimeter). Both 
systems of striae are very pale (schivach gezeichnet), so they cer- 
tainly require an excellent objective for their resolution. Never- 
theless, with oblique light, and on bright days, they can be seen 
with objectives of the highest power almost as well as those of the 
Grammatophora, if the object is only properly prepared, the valves 
separated [gespalten), and mounted dry. In balsam, on the other 
hand, the transverse striae are very difficult to see : nevertheless, I 
have recognized them, even in this case, with the System No. 10 of 
Hartnack." 
During the summer of 1871, a slide of Frustulia Saxonica, 
mounted dry, was presented to the Museum by Dr. J. J. Higgins, 
of New York, and subsequently two other slides, also dry, v/ere 
obtained from J. D. Moller, of Wedel, Holstein. I found no diffi- 
culty, on these slides, in seeing and counting the transverse striae, 
both with monochromatic sunlight and with the light of a small 
coal-oil lamp. The longitudinal striae of Dippel, however, I must 
regard as difiraction phenomena, similar in character to the longi- 
tudinal lines which some have described in the central portion of 
Grammatophora frustules ; they varied too much in their distance 
apart, with varying obliquity of illumination, to bear any other 
interpretation. The transverse striae, on the other hand, I found 
very definite in character. I counted on different frustules from 
eighty-five to ninety to the thousandth of an inch, which agrees 
substantially with the results of Dippel, whose figures correspond 
to from eighty-six to eighty-nine to the thousandth of an inch. 
The frustules themselves varied in length from -0018 to -0029 
inch. 
I subsequently removed the cover of one of the dry slides 
obtained from Moller with the diatoms adherent to it, and 
* See a review of his " Beitrage zur neuern Mikroscopie," in the ' Quarterly 
Journal of Microscopical Science,' vol. ii., new series, 1862, p. 292. 
t ' Das Mikroskop uud seine Anwendung.' Erster Theil. Braunschweig, 
1807, p. 132. 
