Notes . 
577 
a clear account of the Plankton-life of a river, the Oder. His first 
paper on this subject was published in 1897 \ to be followed in 1899 
by a fuller account 2 . In the interval which elapsed between these 
two papers of Schroder’s, Zacharias 3 published a brief general account 
of the Plankton of rivers (so-called Potamoplankton). This paper 
gives the results of Plankton-collecting in a number of rivers (Pleisse, 
Schlei, Trave, Oder, &c.), and terminates with a discussion of the 
probable origin of the Potamoplankton. Quite recently Brunnthaler 4 
has published a short communication on the Plankton of the Danube 
near Vienna, whilst Zykoff 5 and Bolohoncew 6 have described that of 
the Volga near Saratow. 
Brunnthaler also discusses the possibilities of an independent exist- 
ence of Plankton-organisms in flowing water, and maintains that 
in the swift Danube all the Plankton found has been carried down 
from quiet portions of the stream’s course. This view seems very 
probable, and can also, without doubt, be extended to rivers of less 
rapid current. Thus in a river like the Thames many of the 
organisms found floating freely in the main-water of the river have 
probably been derived from higher and almost stationary parts of its 
course. Schiitt 7 opposes the idea of an independent existence of 
Plankton in streams, and maintains that all the individuals present 
have been derived from its stagnant backwaters and slow-flowing 
tributaries. In rivers which flow as slowly as the Thames, however, 
reproduction of the Plankton-organisms even in mid-stream un- 
doubtedly goes on. Pediastrum and Eudorina, two of the commonest 
among the chlorophyceous Plankton of the Thames, were again and 
again met with in every stage of reproduction, and I am quite certain 
that the other organisms reproduce in the same way, but perhaps less 
frequently. Diatoms were often seen in a state of reproduction, 
1 Ueber das Plankton der Oder. Ber. Deut. Bot. Ges. xv, 1897, p. 482. See here 
for further literature. 
2 Das pflanzliche Plankton der Oder. Forschungsber., Plon, 1899. Tell vii, 
p. 16. Recent literature mentioned. 
3 Das Potamoplankton. Zoologischer Anzeiger, No. 550, 1898, p. 41. 
4 Das Phytoplankton des Donaustromes bei Wien. Verhandl. der k. k. zoolog.- 
botan. Gesellsch. in Wien, Jahrg. 1900, Heft 6, pp. 308-1 1. 
6 Zykoff, V. Das pflanzliche Plankton der Volga bei Saratow. Biol. Centralbl., 
Bd. xxii. No. 2, 1902. 
6 Bolohoncew, E. Materialien zur Kenntnis des Phytoplanktons der Volga 
(bei Saratow). Moscow, 1901. (Russian.) 
7 Das Pflanzenleben der Hochsee. Kiel, 1893, pp. 9-1 1. 
