4 
Transactions of the Society. 
that their number increased on keeping under relatively unhealthy 
conditions, argues strongly in favour of the conclusion that these sacs 
really are due to some parasitic fungus and are not proper to the 
healthy diatom. 
Though the gathering made in the beginning of March gave no 
sac-hearing specimens among the thousands of Pleurosigma present, it 
did contain large numbers of a Bacillaria (or small straight Nitzschia ) 
■with very similar zoosporanges to those in Pleurosigma enclosed. No 
other diatoms were affected, though Pinnularia , Cocconema, Amphora , 
Surirella, Campylodiscus and Cymatopleura were abundant. 
If further observations should confirm the first and establish the 
fact that diatoms of different species hear these sporanges only at a 
season peculiar to each, it will be necessary to believe either that 
these spore-sacs are proper to the diatom itself, or that there are a 
number of distinct parasitic fungi, each of which has its own season 
for the development of sporanges, and each of which can only find an 
appropriate host in one particular species (or genus) of diatom. 
I am induced to bring forward these very incomplete results by 
the consideration that, as there is great uncertainty about finding 
the material for confirmatory observations and experiments, it 
is almost necessary that mot e than one pair of eyes and hands should 
be at work on the subject if it is to be carried to a satisfactory con- 
clusion. 
The literature bearing directly on the fungoid parasites of diatoms 
other than the paper of Zopf is almost nil. 
Cornu, in his monograph of the Saprolegnise in the 1 Annales 
des Sciences Naturelles ’ for 1872, describes under the name of 
Olpidiopsis several species of parasitic fungi infesting them. Some 
of these bear considerable resemblance in general characters and 
appearance to Zopf ’s Edrogella and especially to that form of it 
which is described in the present paper. Pringsheim, in Jahrb. wiss. 
Bot., i. p. 289, describes a Pythium as attacking diatoms. 
Carter (An. Nat. Hist., 2nd series, xvii. p. 101) describes a para- 
sitic fungus which attacks Spirogyra , and which somewhat resembles 
Edrogella, but which he expressly says is not found in diatoms. 
Henfrey (Tr. Mic. Soc. (n.s.), vii. p. 25) describes a parasitic 
fungus which seems to be identical with Carter’s. 
There are two papers, by Currey and llabenhorst respectively, on 
parasitic fungi attacking algae (Mic. Jn., v. p. 211, and Babenhorst, 
Alg., iii. p. 276) which I have been unable to consult in the original. 
A. Fischer in Pringsheim’s Jahrb., 1881-2, xiii. p. 286, extends 
and completes the description of the parasitic fungi treated of by 
Cornu (see supra) but does not note the occurrence of any of them in 
diatoms. 
