THE 
MONTHLY MICROSCOPICAL JOURNAL. 
AUGUST 1, 1875. 
I . — Number of Striae on the Diatoms on Mollers Probe-Platte. 
By F. Kitton, Norwich. 
{Taken as read before the Royal Microscopical Society.) 
In the table of measurements of the striae of the various diatoms 
on Moller’s Probe-Platte appended to Mr. J. E. Smith’s paper 
published in the last number of this Journal, Nitzschia curvula is 
stated to have 84 '1 in '001''. As I am well acquainted with this 
form, not only from specimens of Professor Smith’s own gathering, 
but also from many other sources, I felt certain that some error 
had been made. I have therefore examined one of Moller’s prepara- 
tions of the form he calls by this name, and, as I suspected, it is not 
Nitzschia curvula Sm. but his Nitzschia sigma.* The figure in the 
Synopsis is very characteristic so far as the outline of the valve is 
concerned, but the striation (very imperfectly shown) represents the 
striae far too distant. The Synopsis states the striae to be 56 in -001". 
I have never seen any British specimen of this species with striae 
so close as this, and in a gathering from Felixstow they are about 
as easily resolved as those on Pleurosigma quadratum : about 
40 in ’001" I consider to be a nearer approach to accuracy. The 
species sold by Moller certainly has them very fine, and not easily 
resolved with 4th objective and B ocular, but in no respect is there 
any difference of specific value to distinguish it from the British 
form. 
N. curvula of Smith ( = N. sigmatella Gregory, ‘ Quar. Jour, 
of Mic. Sci.,’ vol. iii.). The specific characters in the Synopsis are 
not only obscure but misleading. The description is as follows : 
“ F. Y. linear, tapering towards the truncated extremities. 
Y. linear acute, striae obscure. Almost identical with N. sigma , but 
distinguished from that species by its more delicate striae and fresh- 
water habitat.” It will be seen from the above description that no 
definite idea of this species is obtainable ; no allusion is made to 
the sigmoid form of the valve nor to the pseudo-punctate appearance 
of the margins of the valves ; the remark that it is almost identical 
with N. sigma is also misleading, it really bears no resemblance to 
that form, and the striae are at least as distinct, and perhaps more 
* I have forwarded specimens of both forms, which can be seen at the 
Society’s rooms. 
VOL. XIV. 
E 
