92 
Okeden, on Diatomacea. 
common species. When first gathered, the stipes were quite 
distinct. 
No. 114, 114', Il4fl5, and 1146. I give this as Homosocladia 
filiformis, to which species it most nearly approaches ; still it 
differs from that species in one respect, namely, that whereas 
in the specific description of N. filiformis in the ' Synopsis ^ 
we find " fascicles containing three or four frustules/^ while 
in this specimen the frustules are closely and densely packed 
in large numbers. A reference to the slide marked 141*, 
which contains the Diatom in its natural state of growth, 
burnt on the cover so as to show the threads, will explain 
what I refer to. I have put a ring round a well-marked col- 
lection of these threads. Nos. 114« and 1146 contain the 
Diatom boiled in acid for further examination and comparison, 
and I feel sure that a careful examination of these slides will 
convince any one that this species is to be referred to H. 
filiformis, and to none other. 
Nos. 120 and 120 a. This is the gathering of Achnanthes 
parvula, of Kutzing, to which Dr. Arnott alludes in his paper 
on Rhabdonema.^ I found this interesting species in pro- 
fusion at Neyland, in the March of 1857. I am not aware 
that it has ever been found by any one before or since in 
any British locality. It would be presumption in me to add 
anything to the description given of it by Dr. Arnott. 
No. 121. This gathering is interesting, as containing Nitz- 
schia linearis in a state of conjugation. I have marked on the 
slide several bundles of the Nitzschia, which, when the 
gathering was freshly made, were to be seen surrounded 
with a mucous envelope, and exactly similar in appearance to 
the bundles of Synedra radians in No. 35. This, therefore, 
adds one more to the list (at page x. of the introduction to 
volume ii, of the ^ Synopsis^) of those species in which conju- 
gation has been observed. 
Nos. \%\a and 122. These are interesting, as being gather- 
ings of Amphora minutissima, perfectly free and non-para- 
sitical. A reference to the index to the slides will show how 
widely apart are the localities of the two gatherings; No. 
121 a being from Neyland, while No. 122 is from the Vale 
of Neath, near Swansea. This, I think, goes far to prove 
that A, minutissima is not naturally a parasitic Diatom. 
No. 123. Is my original gathering of Surirella Amphioxus,i 
first pointed out by me to the late Professor Smith, in 1855. 
I should be glad to know whether other observers have 
found it. 
* 'Micros. Journal,' Jan. 1858, p. 92. 
f ' Synopsis,' vol. ii, p. 88. 
