JOURNAL 
OF THE 
ROYAL MICROSCOPICAL SOCIETY. 
FEBRUARY 1893. 
TRANSACTIONS OF THE SOCIETY. 
I . — On an Endophytic Parasite of Diatoms . 
By Charles Haughton Gill, F.R.M.S., F.C.S. 
( Read 18 th November , 1892.) 
Plate I. 
During the late autumn of 1891, while examining some large 
gatherings of diatoms from the New River, near London, in search 
of instances of conjugation, I observed several cases of what I at 
first took to be the formation of sporanges by Pleurosigma attenuatum 
itself. Further observation, however, makes it almost certain that 
the spore-sacs in question are the zoosporanges of a fungus similar 
to, if not identical with the Ectrogella bacillariacearum described 
and named by Zopf,* as infesting Synedra and Pinnularia. 
In general characters they agree with Zopfs description and 
figures of Ectrogella , except in the point hereinafter mentioned, 
and differ in form only as they might be expected to do when deve- 
loped within the shorter, wider shells of Pleurosigma , instead of the 
exceedingly long and narrow Synedra. 
These spore-sacs, as contained in Pleurosigma, , are sausage- shaped 
EXPLANATION OF PLATE I. 
Fig. 1. — Pleurosigma attenuatum with single sporange in early stage. X 300. 
j* 2. ,, ,, ,, two ,, „ x 300. 
,, 3. „ „ „ single „ with beak on the point of 
bursting, x 300. 
„ 4. — Pleurosigma attenuatum with three sporanges, one discharging zoospores, 
x 300. 
„ 5. — A sporange separated from shell and discharging zoospores through beak. 
X 465. 
„ 6. — Cocconema lanceolatum with single sporange in early stage, x 300. 
„ 7. — A Nitzschia with two sporanges before appearance of discharge beaks. 
X 300. 
„ 8. — A Nitzschia with two sporanges with two discharge beaks, x 300. 
„ 9. — Nitzschia sigmoidea with single very elongated sporange. X 300. 
* Zopf, ‘ Zur Kenntniss der Phycomyceten,’ Nova Acta K. L. C. Deut. Akad., 
xlvii. No. 4, p. 145, partly translated by Mr. Karop in Journ. Quek. Club, 1887, 
p. 115. 
1893. 
B 
